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Exercise Care Where You Build Your Deck or Patio: Here’s Why

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The Texas Commission on Environmental Equality (TCEQ) prevents initial house construction from occurring over any point of a septic system.

These requirements include distances from the septic tank and the drainfield from:

  • Foundations
  • Pools
  • Property lines
  • Water wells

Some homeowners, whether accidentally or deliberately, build patio decks or home extensions over their septic systems. This can lead to increased maintenance expenses down the road.

Never build over a septic tank

Never build a structure over any portion of your septic system. Many people don’t know where their tank is located, and 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 their septic tank.

Never build 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.


In our experience, it’s always better to be safe than sorry. Avoid extra expenses and hassles by locating your septic tank before building and steering clear from it with future developments. If you have questions, we’re here to help.

For 86+ years, Van Delden Wastewater Systems has withstood the test of time as the leading Wastewater System company, providing San Antonio, Boerne, and the surrounding Texas Hill Country with services you can count on now and in the future. 

Call us for any of your wastewater systems needs and let our professionals help you with your septic installation and maintenance requirements: 210.698.2000 (San Antonio) or 830.249.4000 (Boerne).

2 thoughts on “Exercise Care Where You Build Your Deck or Patio: Here’s Why

  1. Hi!
    I’m in Georgia and after 20 years of owning my home (the inspection stated I was on a public sewer system) I experienced backup. Contacted the local water company and they said there isn’t any sewer line anywhere near my home. Plumber comes over and checks for the septic tank location and it so happens it’s under the sunroom addition they sold me when I bought the house!
    Needless to say, this needs to be addressed.
    What are my options?
    I don’t like what the plumber recommended, digging a hole, fixing the problem and covering it back up. Then it will happen again!

    • That’s a difficult situation. Are they SURE of the tank location? What “problem” are they fixing? Your concerns are valid that you don’t want it to happen again. We have customers that have built rooms over their tanks and have made a trap door to the lid so that its accessible for pumping. Of course, nothing should be built over the tank, but you may just have to make the best of it unless you are willing to start over with a new septic system or remove the sunroom.

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