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Building Near and Over Septic Tanks

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Building near and over septic tanks

Minimum setback requirements established by The Texas Commission on Environmental Equality (TCEQ) usually prevent initial house construction from occurring over any point of a septic system. These setback requirements include distances from the septic tank and the drainfield from foundations, pools, property lines, water wells, etc.

Some homeowners, whether accidentally or deliberately, build items like patio decks or home extensions over their systems. This can lead to greater expenses when finding and servicing the system.

Building over septic tanks

It is never recommended to build a structure over any portion of your septic system. The most common problem we see is when someone wants to pump out their septic tank but doesn’t know where their tank is located.

It is not uncommon for us to find tanks located under a wooden deck, pool patio, driveways, or even room additions. Most of the time, this happens because the homeowner is unaware of the tank location and/or does not plan for future maintenance on their tank.

Sometimes a homeowner may make removable boards or trap doors that lead under a deck to their septic tank lid for access to pump the tank. No permanent structures should be built over any portion of the system, but at least in this case the homeowner can pump out their septic tank.

Building over drainfields

The drainfield works by absorbing water in the solids and some evapotranspiration. The soil beneath the drainfield needs oxygen so that the microbes in the soil can treat the effluent from the drainfield. However, if a permanent structure is built over a drainfield it can restrict the oxygen flow into the soil and restrict the evapotranspiration process.

A big risk to building over the drainfield is causing the lines to collapse. Also, the soil can compact around the trenches, which may not allow for percolation. Repairing the drainfield or moving it may require an entirely new system depending on your system age and the regulations for your local authority.


124 thoughts on “Building Near and Over Septic Tanks

  1. Great question. If your residence is now connected to a city sewer system, then your septic tank should have been abandoned (crushed and filled in). If the tank was correctly abandoned, then there should not be any issues with building over it. If your tank was not crushed and filled in, then we recommend doing so. Please contact us with any questions.

  2. Hi. I’m trying to gather some information on this very subject. Basically, from what I read above, your only argument against building over the tank (I’m not talking about the field, which is a totally different beast) is that people forget where the access is. Is that all?? I need to put a patio around a pool. The patio will go overtop the septic tank (the field is another 15 feet away and won’t be disturbed). I want to put interlock brick over top of the tank, I won’t add crushed stone or gravel and am aware that will lead to uneven stones, which is fine (I can pull them up and fix as needed). I know where the access is and will mark it accordingly… as far as I can tell, there is NO danger to putting a patio over a septic tank, assuming you know where the access lids are.

    • That’s a great point you bring up. While compromising the tank structure is possible, the most common problem we encounter is with access. Technically, nothing should be built over the tank, especially if there are minimum setback requirements by your local authority. Every situation is different, so I “never say never”. So, to be on the safe side, I would not advise to build anything over your tank. If you are going to anyway, at least be sure you have access to all the lids (sometimes there are more than one that are needed for inspection/pumping purposes). You may even want to have the tank inspected prior to building over it to check for cracks or corrosion at this time. Compromising the structure would be a risk you are willing to take.

  3. I am buying a house in TX with an anaerobic septic tank; prior to purchase I had the tank pumped and risers installed to ensure easy access. Unfortunately, they are rather unsightly. I am considering building a deck over the risers while keeping the access to risers in mind. I am not planning on building over leach field. Are there any considerations I should keep in mind?

    • Ian,

      Technically, nothing should be built over any portion of the system. But, if you do, just be sure all access lids are easily accessible so the tank can be pumped and cleaned. You may want to make sure risers were installed for each lid of the tank. If the house was built after 1987, then there should be two lids on a two-compartment conventional septic tank. Best wishes!

  4. I want to know how close I can pour a cement slab for a patio near the septic tank? I live in Gainesville Florida and need to know how many feet away from the septic tank would be safe?

    • Regulations for minimum setback requirements will vary state by state and even by your local entity. Here in Texas, the minimum distance between a tank and a cement slab is 5 feet. But I still recommend checking with your local septic department for local regulations.

  5. Recently, a friend of mine built a large structure near their septic tank not knowing the setback requirements beforehand. The leach field has not been compromised. The distance from the edge of the metal shed/structure is 3 feet. They found out later the minimum required setback is 5 feet. What problems may arise with the structure being three feet away rather than five?
    Also, for my own education, why is five feet the common distance? Is it for ease of maintenance so equipment and workers can get around the tank for repair? Or is there a structural damage concern?
    Also, when abandoning old septic tanks, do you always have to crush them? or can you just fill them in with dirt? The reason I ask is that if the County makes them mitigate this problem, it may be easier to abandon the septic and put a new one in at the required setback distance. If they have to crush the existing septic tank I am afraid of structural problems to the foundation of the metal shed/structure; so filling in would be better.
    Thank you!!

    • Great questions! I happy to try to help. The setback requirement will very State by State and County by County. The setback requirement in our area is 5 feet as well, but I’ve seen many cases where structures have been built closer to (or even over) the tank without any damage to the tank. I imagine the purpose of the setback requirement is to prevent structural damage or compaction of the soil around the tank which may cause tank to shift and possibly leading to cracks or leaks. Also, there needs to be fall in the sewerline between the plumbing stub-out and the tank. In most cases, abandoning the exiting tank and placing a new one adjacent to the old one is the easiest and best option. In this instance, I would advise checking with the local authority to see if they will require actually caving in the tank or if it can just be filled in. They may offer a variance due to the close proximity of the foundation. Best wishes!

  6. I’d like to build a platform above the drain field that can be used to plant large bushes. Thinking of sheet metal as the base, which would be angled so excess water would roll away. Any concerns or warnings or creative ideas for this?
    I know the posts should be 2′ away from the field.

    • I’ve never heard or imagined such a thing, but it seems feasible. No other suggestions come to mind except to build it high enough so that there can be a flow of air under it to allow oxygen for the soil underneath. I’d love to see a picture when you are finished, or an update after its completed. Best of luck!

  7. My wife and I are looking to collapse and fill a current septic system in order to build on to our existing home. Is there a timeframe we need to wait for the ground to settle after collapsing/filling the tank?

    Thank you!
    Jonathan

    • If you aren’t building anything over the collapsed tank, then it shouldn’t matter as you can always bring in fill dirt if settling should occur. But, if you are building a structure over it, then it would be best to consult with the foundation company. I hope that helps!

  8. I just purchased a home that has a large wooden deck that was built over the leach field area. The deck is elevated about 3 feet off the ground to line up with the back door entrance. I don’t like the deck and I want to remove it and replace it with a brick paver patio.

    Is there any problem with having a brick patio over the leach field? No mortar would be used between the bricks. They would be butted up against each other and sand swept over the bricks to fill in the gaps.

    Thanks.

    • Technically, nothing should be built over the system. A raised deck still allows for oxygen to penetrate the soil, which is important for the drainfield. Brick/pavers, although not mortared together, would likely restrict that oxygen flow into the soil. Although I’ve seen many permanent things built over the drainfield (foundations for garages, sports courts, etc.), I would advise against it to avoid any problems as this may lead to a whole new system.

  9. I would like to add a screened porch. I just had my septic tank cleaned so I know exactly where it is and the porch will not be on top of it. But it will probably be on top of the line from the tank to the house. Suggestions? Thoughts?

    • Its best to not build anything over the line between the house and the tank in case it ever needed repairs so that you could still access it. There are too many scenarios to give a “yes or no” answer. But, if you are going to build over it anyway, I would at least end the porch before the septic tank so that if the tank ever had to be replaced, it can re-connected to the sewerline easily in the future. However, if your sewerline get cracked due to the addition, then it will be much harder to make repairs.

  10. Any issues placing loose patio stones (no mortar) above a septic tank to form a flat surface for a free-standing fire pit? Grass has never grown above the tank anyway, so I’d like to cover the rather unsightly tank.

    • I don’t see any issue with placing the loose patio stones over the tank as long as they can be removed to access the tank during pumping, and assuming the structure of the tank is good (no cracks, corrosion, etc.). However, I can’t advise to have the fire pit over it as methane gas is explosive.

  11. Any concerns with parking a 36 foot travel trailer over the septic other than access to pump it? It would be parked over it permanently

    • I would not advise it. Access for pumping is a big concern. Also, do not drive over the tank as it could cause structural damage, or any of the pipes which can cause them break/collapse.

  12. We would like to build a 8′ x 6′ wooden shed over the septic field. Only 1/2 of the shed would be
    on the drainage line. And it would be raised up on skids which would set on concrete treads. Any advice or warning about doing this would be greatly appreciated.

    • I’ve seen this situation a lot, and rarely have seen major system issues. Its always best to avoid building anything over any portion of the system, so build at your own risk!

    • Here, in Texas, the minimum separation requirement is 5 feet. I would check with your local permitting authority.

  13. There is a long outlet pipe (over 30 ft) connecting my septic tanks to the drainage field. Could I build a patio over this pipe as long as I don’t build over the tanks or drainage field, or would this cause any problems?

    • It’s not advised to build anything over any portion of the system. I’ve seen people do what you are hoping to do without problems, but there are no guarantees.

  14. Hi. My septic tank is right outside my bedroom
    Sliding door. There’s a narrow sidewalk about 2 feet wide between door and tank top (that plastic part that sticks up). I still have to find out about drainage lines but I wanted to lay some bricks to make a patio. I’d like to put in a jacuzzi some day but after reading all these posts about septic tanks I’m thinking it’s impossible. Can I out bricks down over tank? I have to see contractor about jacuzzi idea I guess.

    • We’ve had customers with bricks placed over the tank for patios, but they bricks have to be removed whenever the tank is pumped, and they will never go back in place as nicely as they were originally. Definitely don’t place any portion of the Jacuzzi over the tank. I’d advise having your tank cleaned (if it hasn’t been done recently) and ask the technicians opinion once he can visually see your situation.

    • I’m assuming “drainfield reserve” is meaning that you have a place for a new drainfield should your existing drainfeild fail. If this is the case, then I would not recommend building anything over it, otherwise, what will you do when your existing drainfield fails? Some permits require the “drainfield reserve” to be kept as a reserve, so you may not be able to if its permitted that way. If you do build there, first check into other system options with local installers so you have a plan for the time when your existing system fails.

    • Courtney,

      Thank you for the rapid response. I was hoping for a different answer. However, I think your advice is the best way to proceed.

      Thanks again. I hope all is going well.

  15. This is all very helpful – thanks for all the answers! If there’s a tank close to the house & I’d like to put in a full outdoor kitchen/patio, it seems like the only real responsible option is to move the tank (and retaining clearances for the connections to access any leaks/etc). So the question – How hard is it to move a tank (or do just crush/fill it and put in a new one), and how far can the tank be from the house? (I’m in Southwest Austin, property has good “gravity” as its on a hill, with the tank & fields all below the house). We’re new to town, my tank in CT wasn’t very close to the house, assume that’s fine here also (esp with the gravity assist here, that was a flat lot)…

    • Moving the tank may be possible, but requires a permit. Depending on the age of your system, moving the tank may not be allowable without upgrading the whole system to meet current regulations. I would suggest contacting a local septic designer/installer to see what the options are for your particular circumstance.

  16. Hey, Courtney:

    I was looking to build or erect a simple fire pit on top of my leaching field: it would be a wheel well from an 18-wheeler surrounded by a load of gravel on which I’d put simple chairs and end tables.

    The whole thing would be easily removed if I needed to dig, and I’m not thinking it would obstruct oxygen or weigh too much. Still, risk.

    What do you think?

    Thank you.

    • I would be hesitant to do this, my concern is the heat may penetrate the soil and into the absorption area. I’ve seen fire pits over drainfield areas before, but can’t advise it if you want to be on the safe side.

  17. I have a new above ground leach field here in eastern, North Carolina, the only problem is its in the darn middle of my yard, and takes up a lot of space. It wasn’t graded correctly so I get a lot of rain water draining into my garage. What are my restriction inasmuch as planting on this leach field, I will not plant trees, but flower and such, what is recommend, and I will not dig, maybe build some planter boxes.

    • Above-ground leach fields are not common in our area, so I don’t have experience with your circumstance to offer sound advice. I would suggest contacting a local septic installer to find out.

  18. building a house and noticed this. Is this a septic tank? It’s in the very back of the house but there will be foundation over it.

    Excavators are filling in with rock it looks like. any problems with building over this after it’s filled in? Problems with settling, safety/waste hazard? I assume it’s fine once it’s filled in? Does it have to be pumped beforehand? Any issues with the leach fields? We are connecting to city sewer so no septic tank is needed.

    Looks like a 5,000 gallon septic tank?

    Thanks, as I don’t know anything about septic tanks obviously!

    http://postimg.org/image/9ul3vjlmp/
    http://postimg.org/image/ruas4fgjh/
    http://postimg.org/image/vesgsnj9x/

    • It looks like a tank of some sort, but the pictures don’t show evidence of sludge, so I’m not totally convinced it’s a septic tank. I would recommend calling a foundation company for their recommendations on what materials to fill the tank with and to see if they need to take extra steps to ensure the foundation will be sound.

  19. We want to build a patio extension with a portion of it being enclosed with screening the only problem is the lines/ drainfield run across the backyard at an angle that makes it impossible to really do anything without avoiding building over it. The new structure would not interfere with the tanks themselves. Are there any low risk options for working around this? The height of the decking for the porch would be 3-5″. Would it make a difference if the parts of the deck over the lines were lower like if we did a step down from the higher parts? Environmental suggested cantilevers to add about 2 ft. to the space in either direction but I just feel there HAS to be another way around being stuck with a teeny porch somehow? Thanks in advance!

    • Without looking at the yard and what you want to do, its hard for me to give sound advice. Cantilevers are a good idea. The most important thing is that no deck posts go into the drainfield. If you really want the large deck, you just have to weigh the risks. Best of luck!

  20. We have a cabin in the North Georgia mountains that was built in 2008. Can we put a fire pit (not dug down only bricked around) over the septic area?

    Thanks

    Keith

    • I defiantly wouldn’t do this over the tank. I would be hesitant to do this even over the absorption, my concern is the heat may penetrate the soil and into the absorption area. I’ve seen fire pits over drainfield areas before, but can’t advise it if you want to be on the safe side.

  21. Great site, and great job answering questions in an area where many homeowners lack a lot of knowledge, including myself.
    I am planning an outdoor kitchen with a sink and dishwasher between the house and septic tank. To accommodate it I am extending the patio (concrete slab and flagstone) over the sewer drain line. I have two questions.
    1. Is there any way to further protect the sewer drain line from the weight? (frame it in underground concrete blocks, for example) The sewer line already runs under the existing patio that I’m extending, but as the ground slopes slightly away from the house, I imagine its depth becomes shallower the farther I get from the house.
    2. I would like to know if it is possible to attach the sink and dishwasher drains directly to the sched 40 sewer line.
    Thank you for your time.

    • Thanks for the compliment! I’m happy to help, although a lot of questions posted here are very situation specific and every local authority has different regulations. What we would recommend is to re-lay the sewer pipe with heavy schedule 40 PVC pipe, then sleeve it with another schedule 40 pipe, then bed it with pea gravel. At that time, the other plumbing can be connected to it. In Texas, this requires a permit. You may want to contact a local installer to get the scoop on local regulations or to take a look at what you have to make an on-site assessment.

  22. We are thinking about building an additional room to the front of our home, but are worried about getting too close to the leach bed. We would like to go out 20 feet which would put us about 3 feet from the leach bed. Would this be too close?

    • I would recommend checking your local regulations. In Texas, the minimum setback requirement is 5 feet.

  23. Hello, I have a couple of questions and was hoping you could help me out. First, what is the best method for identifying the edges of the leach field area. I have the original permit application from 1979 but there are very few measurements. I do know the edges of the septic tank itself. Second, I want to level my back yard a little bit by adding approximately 1-2 ft of soil on top of the leach field. With a 35 yr old leach field, should I worry about compaction from the extra weight of the dirt.

    • Unfortunately, there is no good way to know exactly where the drainfield ends and begins without an as-built plan and without being able to visually see it by dips in the yard or lush green grass strips. You can try to dig, but sometimes that’s like finding a needle in a haystack. Plus, digging into the drainfield can cause damage, so I don’t recommend that. People add soil over the drainfield all of the time, but that doesn’t mean it should be done. Compacting the soil is on thing, plus the more soil over the drainfield, the less oxygen flow that will get to the drainfield. Your system is older to begin with and one day you will need a new system. If you want to chance adding the extra soil, then you may just speed up the need for a new system.

  24. How near to a drainfield can I safely dig a root cellar? I live on a south-facing slope and I’d like to dig a root cellar into the hillside just below my drainfield. Thank you for your wonderful site by the way.

    • I’m happy to help where I can, but I’m afraid I’m not much help on the topic of root cellars. They are extremely rare in our area and I’ve never come across one myself. I would recommend calling a local septic installer or the local septic permitting office to inquire about regulations for that. Best wishes!

  25. Hi, thank you for the article. It was helpful. In my case I don’t have much room for the septic tank and leach field to provide 5ft of clearance from the house :(. The house is on concrete foundation and I have just 16.4 ft by 65 ft area in front of the house for the tank and the leach field. I am not much worried about the septic tank, i’m having it built from concrete. What are the dangers of leach field being so close to the house?

    Thank you!

    • The wastewater filters into the soil not only at the bottom of the trenches, but also through the side “walls” of the trenches. This is the main reason for the separation between absorption area/leach field to the house. You may be able to get a variance, but that goes into design and permitting, which hopefully you are doing. Best of luck!

    • It depends on your local regulations. Our local regulations state that there should be no permanent structures over any part of the system. What you are describing does not sound like a permanent structure to me. If you still get air flow under the storage building then the soil can still get oxygen.

  26. I am looking to purchase a house in Indiana. Currently there is an active septic system with four fingers. A septic company checked it out and said the system was in perfect shape. The problem: it sits below a garage built in 1977. It has an access unit right at the front of the garage. We are trying to figure out if this has been grandfathered in or not. Or if it is even legal to buy while under a garage. Can you advise?

    • The only one to determine that for sure would be the local permitting authority (in Texas, its usually the County septic department). They will be able to tell you if its grandfathered in or not. I will say, we see this all the time. Not that it should be over the tank, but the system may still be able to function. So, there’s a functioning standpoint and a regulation standpoint. If you don’t know who to contact, try calling a local installer to see who permits the systems in your area and that’s who I would call. Good luck!

    • Thank you. I have pulled the permit for when they built the garage over it in 1977 and the permit is good. I will go from there.

  27. We bought this house 3 years ago in Texas. They really showed off the new septic tank when we bought it. Fast forward 3 years, my windows are hard to open, the tiles are cracking, the wall has cracked. My house is sinking. We located the old septic tank. It is right in front of the house. More than 5 feet, but we think the drainage lines are running under my house. What can we do legally? Can it even be repaired? It’s foundation. Who is responsible? Thank you for the help.

    • Did you get a real-estate septic inspection when you bought the house? At this point, I would recommended contact a local installer/septic inspector to locate system components and contact your real estate agent to see what your options are.

  28. i have read a lot on this page!! a lot of useful information and i am thankful for that!! i just bought some land that has a septic system on it, i am moving from the city, so this is new to me. i want to build a house eventually and want to know what is common for the space between the house and the clean out pipe?

    • Usually, the cleanout is within the first 5 feet of the house, but they can be further. You might have local regulations regarding the specific cleanout location, so I recommend checking with a local installer.

  29. I want to build a section of sidewalk to connect my patio to my driveway. I will need a section of the sidewalk to go over the pipe leading from the house to the septic tank. We moved into our home in July of 2015 and have a very sandy loam soil. Would it be ok for this sidewalk to go over this pipe leading from the house to the tank?

    • Putting a sidewalk over the sewer line that connects the house to the tank is typically not a problem. You will need to be sure the sewer line does not get damaged from framing the sidewalk, or get damaged from the pressure of the sidewalk. In the State of Texas, you are supposed to sleeve the sewer line under the sidewalk with sch 40, unless you have schedule 80 pipe already installed. At minimum, you should expose the sewer line in a couple areas to locate it before framing, and also check to see the schedule/thickness of the sewer line, to help determine the best option for your particular situation.

  30. We are thinking of putting a small deck over our septic tank covers. We would screw the deck boards, so when we clean our septic tank every two years, there would be easy access. Does this sound like something that could be done. Right now they are under patio stones and we have to lift the stones, dig up the dirt and remove covers for cleaning. That’s why we think this might work. We thought about putting in risers with a new cover also instead of the concrete ones. Any opinions?

    • Local regulations do not “allow” for any structures to be built over the system, however, we see decks over tanks all the time. If you are going to go ahead and build the deck, you don’t want to have to dig once the deck is over the lids. You want the boards to be easily removable. Some people put in “trap doors” with a hinge so its super easy to gain access. Also, be sure the deck support boards do not rest on the tank.

  31. I live in Arizona and looking at retirement places. I found a house I really like that is in the Gila county country side (by Payson). The problem is the owner told us there is no cleanout. As the conversation went I found out the addition of the house is built on the septic. The leach field is not covered, but the entire septic is under the house. We could buy the house and in the future install a new septic system. The owner said she had a guy out to look at it and he put in a camera to locate the tank, he said all was good and she should fore see any problems, except there was no cleanout.

    My question is if we do buy this house, if we end up putting in a new tank, will the old one not collapse or let off fumes? I really like the area and the house (and the price)

    • There’s a lot of things to be addressed here. First, you need to contact someone that knows the regulations locally for this property. Regulations vary by state and by county usually. OUR regulations state that no permanent structures should be over the tank. However, we do see additions over the tank often. The tank should be pumped regularly so in those cases we recommend that there still be access to the tank. OUR regulations would require the tank to be crushed, filled, and abandoned when a new system is installed – so if that’s the case for your regulations – how would that occur? Just something to think about. Anytime you purchase a home, it is recommended to get your own inspections to do your due diligence. Be sure that your inspector knows the LOCAL regulations for this property so you really know what you will be facing should you purchase the home.

  32. I would like to build a carport along side my house. The deep soil structure around my house is all gravel. When I dug the hole for the second footing for the two support post needed. I discovered wet gravely soil at the two foot level. I have concluded that the source for this wet gravely soil is from my septic drain field pipe two feet away. My building engineer states that each support post will have eight thousand pounds exerted on it. My question is, if I place the carport footing in this wet location will the structure slowly settle and sink over time? If your answer is yes, my idea to solve this problem is to dig down and replace ten feet of perforated pipe with solid pipe five feet on either side of the footing to keep the area around the footing dry. Then I would extend the existing drain field ten feet with perforated pipe to account for the loss from the substituted solid pipe used around the footing. Will this work or is it even needed? Or do I just place the footing in the septic drain field?

    • That’s are hard call. Have you consulted with an engineer about putting the footing in this wet location? I cant imagine it would be a good idea. Also, you don’t want to give a pathway for the effluent to surface. On the flipside, OUR regulations here would require moving the drainfield line and possibly replacing the system depending on several factors. I’d call an engineer and a local septic company.

  33. We’re building a 1,400 square foot house (cabin) for recreation and retirement. It’s on the James River in central VA and the septic/leach field system is huge! We’ve had to have lots of trees removed and we’d prefer to not get into the grass cutting mode.

    So we were thinking about a mulch covered labyrinth of some sort…with annuals and perennials around the pathway. Maybe a small seating area in the middle. Is this ok? Also, are azaleas okay to plant on or near the leach field? I know they have a shallow root system, but not sure how shallow they have to be.

    • Your plans sound very nice. I don’t really have a green thumb, so I can’t say which plants are OK. If they have shallow root growth it MAY be ok, but no guarantees. Maybe contact a landscaping or nursery company to see if they have any thoughts/experience with what to plant over the drain field. Its always best to lean on the side of caution and not plant anything over any portion of the system, but if you are set on doing it, then I’d probably consult a nursery or landscaping company.

  34. Background: We live in an area that has mostly clay soil. Our frost line is at 36″. We built our house in 2005 and had the septic tanks and sand filter (our land failed a percolation test) installed by a local professional. We have the tanks serviced regularly and according to the company that pumped them last spring, we won’t need to have it done again for 7 years (it’s just my husband and I and we sized the tanks and sand filter for 4 bedrooms plus a garbage disposal). We have a hard time getting grass to grow over the tanks and it looks unsightly. The rest of our nearly acre lot looks gorgeous and this area sticks out like a sore thumb. This has been an issue for over a decade and we are determined to fix it this summer! Our plan is to put a natural stone patio (with ground cover growing in the gaps between the large stones) over the tanks and a large pergola on the patio. The pergola will straddle the tanks. We know exactly where the access hatches for the tanks are and will put a smaller stone over those so we can pull them up when the tanks need to be pumped and inspected. The soil over the tanks is currently 12″-18″ but we will need to level that area for the patio. We will be sure to maintain 12″ of dirt. I know this plan wouldn’t be recommended but, do you have any suggestions to help ensure the safety and longevity of our tanks? We will be putting in concrete supports for the pergola, but not to the recommended depths of 36″. (We have hopefully devised a plan to overcome heaving from the freeze and thaw without going to below the frost line.) The sand filter is probably at least 10′ from where the patio will end, but the pipe that runs from the tanks to the sand filter will be under the patio. (Sorry for the long post, but I was trying to give you as much pertinent information as possible.)

    • Thanks for all the info. We don’t have frost here in San Antonio so I am not experienced in dealing with that. Nor do we have sand filters (except for some commercial type systems), so I’m not equipped to comment on either of those factors. However, here’s a few things off the top of my head: be sure the tank access lids are accessible and that no structures are placed over or too near to the tank. Every state/county has different setback requirements. Have you consulted with a local septic system installer? That would me my next step if I were in your shoes.

  35. WE HAVE AN L SHAPED LOT WITH THE HOUSE AND THE GARAGE ON THE TOP 2 LOTS AND THE SEPTIC TANK AND FIELD ON THE 3RD LOT. IT APPARENTLY HAS BEEN “FAILING” FOR THE LAST

    We have an L shaped lot with a house and garage on the top 2 logs and the septic tank and field on the 3rd lot.
    we would like to separate the 3rd lot and install a new septic system for the top 2 lots for the house. How long before we could build again on the 3rd lot (assuming we abandon the existing system – or maybe there’s something else we should do?)

    • You might want to check into local regulations to see if there are any specific rules for that. Will you be building over the drainfield? If so, you might want to check with your builder or engineer – I’m not sure if/how that might effect a structure.

  36. Hi… how about putting some removable (plastic, from Ikea) tiles down (probably with some sand or gravel to make it level first) on top of the tank. They snap together so no mortar or anything permanent. We have 2 lids and I’d really plan to try to only cover up one with this “patio” if possible.

    After you give me your thoughts on that, tell me what you think of placing a 10 by 12 foot aluminum gazebo in that general vicinity? One foot will very likely rest above or next to the tank. Thinking of anchoring 3 of the legs in the ground but not the one above the tank. Thoughts? Advice? We have a teeny tiny yard and this is really the only place for such a structure.

    Thank you!

    • I’m surprised you are on a septic system with a teeny tiny yard. That might be ok if the plastic and material underneath are easily removable – just keep in mind that it will have to all be taken up each time the tank is pumped. If its a two-compartment tank, then both lids will be needed each time. Everything is circumstantial. Its not recommended to place any of the support for the gazebo over the tank. Also if the tank will be under the canopy of the gazebo, that means you will be walking/sitting under it. While you would assume the tank is sturdy enough, tanks can corrode, and I’ve seen them corrode to the point of being a safety hazard. So unless you have the structure of your tank inspected regularly (which also means tearing up your plastic regularly), I’m hesitant to recommend the gazebo.

  37. Hi from Washington State! We have purchased a two story home with a postage stamp size deck exterior to the dining room on the second floor. The deck stands about 9 feet high. We want to enlarge the deck substantially and we are struggling with how to place supports around septic tanks that are located close to the house adjacent to the footprint of the current small deck. We want to continue the 9 ft height over the tank portion of our system, so accessing the tanks for clean out won’t be a problem. A septic cleaner guy said we would likely be safe putting an above ground support where the 2 tanks (we have a 5 stage system) butt up to each other because it is basically a double cement wall. The other supports will be sunk in spots that aren’t occupied with other aspects of our system (drain field and sand field). I understand it would be ideal to not build anything over the system, but we really need a bigger deck. Thoughts? Thanks so much!!

    • Hi! This is a tough question because without seeing the property and the plans of the septic system, its hard to imagine and give advice on. We don’t have 5-stage systems around here – so that makes it even harder for me to imagine. I’m sorry I’m not much help! I think I’d get a 2nd opinion from a local septic company about installing any support over the tank. Regulations may be different there for tank structures – I wouldn’t recommend it here – but tanks may be build different in Washington. Thinking LONG term….what if those tanks need to be replaced and the support for the deck is over it?

  38. I am think of building hey Intex above ground pool over at the far Corner section of my septic finger system. Would this be a good idea even though it will be taken out during the winter time?

    • This would never be a “good” idea. That doesn’t mean people don’t do it. Some state and local regulations prohibit placing any structures over the tank. Soil compaction should also be considered as well as the weight over the drain field.

  39. Our septic tank is right by our front door. We’d like to install a stamped concrete walkway going from the driveway to the front steps, but it would require us putting the walkway over the septic tank – there’s no way to avoid going over it. Access to the cleanout won’t be a problem – we would arc around the cleanout – but will the weight of the walkway (as well as the installation, which may require some equipment) be an issue?

    • We often find that owners have built walkways over their tank. Most of the time, we don’t find issues with the structure of the tank, however, the actual lids to the tank need to be accessible. Pumping cannot be completed through the cleanout. Some tanks have several lids that need to be accessible due to dividing walls inside the tank. If the walkway will restrict access then you’ll end up having to remove it eventually. That’s probably not what you wanted to hear 🙁

  40. we bought an old (1967) house about 8 years ago, and the owner said they used a lintel? to support the foundation of a new addition they had made. it is over part the tank. never had a single problem with this system and treat it regularly. just wondering if a pump out can be accomplished through a clean out on a single tank system (pre 1980’s)?

    • The septic tank cannot be pumped through the cleanout, it must be pumped through the access lid(s) on the top of the tank. “Treating” a septic tank does not prolong the periods between cleaning the tank, which usually should be done every 3-5 years on average. We run across tanks located under additions, sometimes if the tank is not completely under the addition we may find a lid that is accessible on the outside of the addition, but sometimes not. Sometimes access has to be made through the foundation by cutting it – which is an undesirable situation. Otherwise, just use it as it is, but when the system fails, access will still be needed to connect the plumbing to the new system in most cases.

  41. Hi, I’m reading a lot of great advice from your blog comments! Thank you for posting. I’m looking to buy a used home in GA. It is near a lake, and has a downhill slope from front to back, and a dry creek at the left edge.

    While doing a “should I buy it” look around inspection I found a small hole in front of the septic tank closest to the house. The hole was only about 2″ in diameter. I put a stick into it and it went down 36 inches deep and appeared to be about 12 inches wide. Lightly stepping around it, there appeared to be some give around the hole. I didn’t want to break the sod up by pushing harder (or falling in!). The house was built in 1974. To the best of my knowledge, only one toilet feeds this 500 gal tank. There was some softness on the outlet side of the tank nearest the drainfield, but I found no holes near the outlet, to the best I could determine..

    I’m guessing I will need a county health inspection before buying the home, is that correct? I’m not sure if I also need soil inspections, but now we’re suspicious. The house has now been empty for 6 months, I’m not even sure what or how to tell the owner about it…

    There are also some French drains around the property located at the low point in the basement, and it appears water came into them at some point into the room, but the owner claims it was from the gutter overflow. The home cinder block foundation that has settled some (somewhat normal after 40 plus years) and a 6 ft by 8 ft concrete pad nearby that has cracked, but is over 5 feet away from the tank. Foundation inspectors

    Final question, there is no room I can determine for a reserve drain field. The home is on a lake, and I’m worried there’s no do over there for a drain field, but wondering/hoping the current systems could be viable (there’s another system in the front of the property for the main floor).. The owner insists they will make no repairs and wants to sell the house “as-is”. This is a tough one to swallow. I’m willing to walk away if there’s too much risk involved. The house, like I said is over 40 years old.

    What would be possible causes of this, where there’s a void immediately towards the house side of the tank? I’ve thought maybe it was a leaking toilet, but that’s not the case. I’ve searched the internet quite a bit and find mostly problems on the outlet side. Considering the age of the system, could it still be repairable? Should I report this situation to the county health board myself?

    Thank you, very much, for any help you can provide me and your clients. I know there are a lot of questions I’ve posed here.

    • Hi! A lot of your questions are very hard to answer without knowing specific regulations in your particular area. Check with GA to see if septic inspections are required, and if so, who performs them. I would get a professional septic system inspection for yourself to see what is going on. You might call the local septic department/health authority to see if they do inspections of any kind. Here, there are no regulations for septic inspections but other states do require tem. Also, here in TX, the septic department does not perform real estate inspections, but they do enforce regulations. So if there is a safety or health hazard, then contacting them might aid in doing some negotiations with the seller. If there is a problem, it is likely that they have to disclose it to the next buyer and then they are taking a chance that the next buyer will actually accept the septic system “as is”. Its likely that the existing system does not meet current regulations – and being that this is waterfront property – a different type of system may be required (such as an aerobic system) which might answer your question about a reserved area. A lot of it comes down to your local regulations. I wish I could be more helpful but I don’t want to make any assumptions. Best of luck!!

  42. Thanks for following up with your keen insight. Although I might jeopardize the deal, I don’t want to buy a turkey. I’ve made a counter subject to a soil and septic inspection by certified mail. I’ve heard no answer, but will be calling the local health department for inspection and advice. Since this is the house next door to us, these conditions could possibly affect our own property just as well. We thought the purchase of it would be a good idea for extended family to live immediately close by, but we certainly don’t want to buy an unknown problem or a money pit. Best regards, your advice is received invaluable. Anything further you can provide is most appreciated, and I think you’re doing a great service to people with a potential heavy load staring them in their face. I know it’s not rocket science, but code and the systems required wasn’t taught in high school. Thanks again, keep it up!

  43. Hello, this is a fantastic site providing excellent information on septic systems. My question is this. We have 5 homes each having its own septic tank but we share a 3 acre common drainfield. The current septic system has been in operation for 25 years. We will shortly be connecting to the City’s public septic system. As such we were thinking of selling off the 3 acres which was used as a drainfield so as to build a home on it. Is this a feasible thing? Can you build a home on a recently abandoned drainfield? (Our laterals are 10′ deep) Thanks in advance. Jon

    • It would not be wise for me to make any assumptions. I recommend that you contact the local septic department to see what your local regulations say about that. Each state and county has different regulations. Good luck!

  44. We have a deck built over out drain field. It’s about three feet or more off the ground. It’s large and I really like it. When it comes time to replace the drain field can I request a new drain field site instead of dismantling and moving the deck away.

  45. Great site you’ve set up here! I’m looking at a small property wth tight setback constraints and the city has said that i’ll need an advanced on site treatment system. Getting creative, I was thinking about building the cottage one level up on stilts and leaving the entire ground plane clear. Then I could tuck most or all of the dispersal field under the structure, but still have full access to the system and not block the field’s oxygen supply. Do-able? I’ll definitely be consulting a professional, but was curious if this is something you’ve ever seen? Thanks!

    • That is being creative! I don’t think they would allow that with our local regulations, so it will probably depend on what is allowed where you live. But, let me know when you find out! I’m curious! 🙂

    • I’m not sure what you mean by “to replace my lawn”…but generally, a small decorative rock over the leach field should not be a problem.

  46. We are building a deck off the front of a prefab house. We wanted to go out 12 feet on the deck and another 3 feet for a ramp going along the entire face of the deck. we hit water when we dug down about a foot at the 12 foot mark and then hit the drain field when we went another 3 feet out for the ramp. My question is, is there any way to do footings for a regular deck even at the edge of the drain field? I am not sure what the regulations are so i will check on that but wanted to know if you could even do it.

  47. I want to place a small concrete slab (2 1/2′ x 3 1/2′ X 3″ deep) on which to put a portable electric generator near my septic tank. I have dug around the tank to locate edges but don’t know how deep lines from the house to the tank may be. Can you advise?

    • Usually several inches, at least, sometimes up to a foot. Every situation is different. There has to be enough fall from the house to the tank, but it might also depend on the slope of the ground, how deep your plumbing stub out is, and how deep the tank is. That doesn’t really help you much. The only way to know is to locate the pipe itself (by probing or digging).

  48. We put a 12 x 20 shed on our property in may 2016. It sits above the ground about 8 inches and runs the with of the last (end) 10 feet of 3 out of 4 of the leach legs. This is our first encounter with a septic system and we’re not informed as to any does and don’t. We had the system cleaned out yesterday and were told there were roots from one tree encroach into the system at the pump site. no big deal he removed the roots and, we are taking the tree down next week. 1 problem solved. However the position of our shed seemed to be a major problem to the person cleaning g out the tank. He warned us to get the shed off the end of the leach field. His reason: the sun needs to hit the whole leach field. I was ready to burn the whole shed just so the sun would be able to hit the ground. We have already customized the whole sheds interior. How much risk do we take by leaving the 8 inch elevated shed over the end of 3 legs of the field?

    • The main reason permanent structures should not be over the absorption area is so that oxygen can get to the soil. Oxygen is required by the microbes in the soil to treat the wastewater. Of course, there are no guarantees with anything, and no structures are supposed to be over the system, but it sounds like there is SOME room between the ground and the shed for oxygen to get to the soil. Will it cause a problem? No one can say for sure, but it doesn’t sound like an emergency where you need to burn the shed down, just consider moving it at some point. Best wishes!

  49. Hello Courtney,
    I just found old concrete septic tank (emptied, but not collapsed) in the area where I want to build an addition. I was told by some, no need to collapse it, as it has 4-in concrete walls and new footings for my addition should be close to the edge of the septic tank (but still above the tank). If I pour 6-8 inch of new concrete, I see it safer than collapsing old septic tank and not compacting fill perfectly.
    What do you think?
    Mike

    • Not sure where you live, but regulations in Texas would require the tank to be properly abandoned (crushed/filled). You don’t want to create a problem for re-sale of the house either if what you want to do is in conflict with your local regulations.

  50. Hi
    What about building a slab over the lateral that connects the dosing tank to the distribution box? My understanding is that it is a 4″ PVC pipe connecting the two. I would not be building over or near the septic tank, dosing tank or distribution box or drain field. Only the lateral.
    I can’t see a 4″ piece of PVC pipe ever failing. And if it did I believe it would be possible to route a new pipe around the slab – although it would then have a slight bend in it instead of a straight line between the two

    • In most states, you are not “allowed” to build anything over any portion of the system. Or in some cases, you can have the pipe sleeved. It’s a chance you are taking. If you have a back-up plan, that’s better than most.

  51. We are in escrow on a 1.5 acre property in southern California that was built in 1979. According to all records at the city, we have found permits for a seepage tank. However, when the septic service company came out they told us we have leech lines. If there actually are leech lines, someone planted a citrus grove over the top of them. (who in their tight mind would do this?) First question, is there a way to determine exactly what we have without digging up the area?
    We have located the septic tank and know the relative vicinity of the supposed leach lines and know the vicinity where the city knows of a permitted seepage tank. All of this being said, before we go through with the purchase, we would like to know if we can build a tennis court. According to the city and the location of the seepage tank (they are aware of) there is no issue whatsoever, but if we I am concerned about the possibility of leech lines.
    I am well aware that we can not build over the septic tank and/or the leech lines, but what is a safe distance from the leech lines to build a tennis court without sacrificing the efficiency of the septic system or ruining a new court? Thank you so much!

    • Any “safe distance” to the leech lines would be misleading because your city/county probably has actual regulations for that setback requirement. I would get back into contact with the office that you obtained the septic records from and ask them what the setback is. The other issue is you really don’t know where the leech lines begin and end. Without an accurate drawing, its any ones best guess.

    • It depends on your your local regulations, which will also factor in the existing system size. In general, connecting a second home to a septic system that was sized/permitted for a single home will not be acceptable. But, contact your local permitting office to see what the rules are for your particular area.

  52. So we’re building an addition in Virginia and on excavation for the footings the builder discovered the distribution box.
    Inadvertently his excavator broke the lid, but they have replaced it and then they poured the gravel and the concrete footing right on top of the distribution box. His logic was that the box was designed to hold the pressure of soil above it, so the footing should not compress or alter the box function, and that to avoid this we’d have to move the distribution box which would involve probably a new drain field as well. We could pay for a new box and drain field now or we could see if this works and maybe not have to. If it doesn’t work then, we’re back to installing a new distribution box and drain field later.
    Lets keep in mind that the structure and footings are not at all near the drain field but I still think there’s a structural concern with a concrete footing on top of the distribution box which might compress and alter the support to the footing. Am I unreasonable?

    • I don’t think your concerns are unreasonable. Per TCEQ regulations (Texas regulations for septic systems), no part of the system should have permanent structures over it. I don’t know where you are located or if building over any part of the system is allowed, but based on our local regulations I would not recommend it, even if I thought the box might hold.

  53. We’ve lived in our house for 5 years now and I was told (not verified) that the septic is under the concrete garage floor that someone added on at some point. The house is very old (1920) and I worry about servicing the tank if it even is a tank. Is there a way to find out myself where the tank or structure is located and if it is indeed under the garage floor can it be accessed somehow to drain it?

    • One way to find out is to use a “locator”. There are many kinds, but we usually use Prototek locators. Its a transmitter that you flush and then you can pick up the signal, even if the tank is under concrete (in most cases). The negatives are: 1) the transmitter will go as far as it will flush – so if you have any possible obstructions between the commode and the tank, that’s where it will stop; 2) if the transmitter makes it into the tank, it does not indicate where the lid is on the top of the tank (assuming there is one). If you can find a company that can come use a locator such as this, it might be a good first step. Best wishes!

  54. Hi,
    Days before Christmas my leach field failed. It is in my front yard along with the septic tank. A new leach field was put it on the opposite side. A year and a half ago we spent a few thousand on sod. It failed due to trees not allowing enough sun light through. My whole front yard is dirt. We have been looking into hardscape. Now I’m finding out you can not hardscape over a leach field. A switch was added to the septic so that in 10 years or so we can switch back to the old leach field if we have any issues. I keep seeing no pavers, weed cover or mulch. What about gravel on top of the leach field? Would this be too heavy? I really don’t want to try grass again but realize it may be my only option.

    • What you are reading is correct. Its best to have vegetative surface (grass) over the drain field. Grass will prevent erosion, and help with treatment through transpiration.

    • I would not recommend it. You don’t want to build anything heavy over the tanks or put anything structural over the tanks. What are you using the shed for? Storage: remember to not put anything heavy over the tanks and that they need to be accessible for pumping. Livestock/horses: Their weight can cause the tanks to cave in.

  55. About 2 weeks ago there was a cat stuck in a tree in my neighbors yard. The fire department sent a large ladder truck to get it down. When I went outside the truck was in the neighbors driveway which is right next to my drainfield. I watched for a bit then went back inside. The next day I went out and found large tire tracks over my drainfield. Apparently, they moved the truck to get at the cat. This happened a day after a good rain so the soil was very damp and compatible. Should I be worried?

    • Driving over the drainfield can damage the lines and compact the soil. I’ve seen drainfields fail from driving over them, but I’ve also seen drainfields working just fine after they were driven over. Should you worry? Its hard to say. Of course driving over the drainfield is never recommended, but I cant say if it did any damage. You might want to have someone come look at it and also check the level in your tank to see if the liquid level is normal (indicating the drainfield is accepting wastewater).

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