We often receive calls about “full” septic tanks. But what does full really mean?
A septic tank should always be “filled” to its normal liquid level, or the bottom of the outlet pipe which carries effluent to the absorption area. This normal liquid level is usually between 8” to 12” from the top of the tank on average (see picture at right). If the liquid level is at bottom of the outlet pipe, then one would assume the absorption area is accepting the household wastewater.
If the liquid level in a septic tank is above the outlet pipe, or to the top of the tank, we call it “overfull” because the tank is filled above its normal operating level. If the tank is overfull, this is usually a sign of problems with the absorption area.
We have a lot of people call us to pump their tank because they say it is full…usually because they are beginning to experience problems. Sometimes, though, the problem is actually with the plumbing. How can you tell if a problem can be solved by your septic maintenance provider or a plumber?
If the problem is due to backup in the house, we recommend checking your cleanout between the house and the tank (if one is present and accessible) to see if there is any backup in the cleanout (usually a 4” PVC pipe that has a removable cap).
If the cleanout does not contain any backup, then we usually recommend contacting a plumber, as this indicates the wastewater from the house is not making it to the cleanout.
If the cleanout does contain backup, then it’s a 50/50 chance it may be the septic system. This can then be determined by exposing the lid(s) of the septic tank and checking to see if the liquid level is normal or overfull. If it is normal, we usually recommend calling a plumber. If it is overfull, then you may have larger issues (i.e. the absorption area).
If you do not have a cleanout, then your chances may be 50/50 whether a plumber or septic company is needed and you won’t know until one of the two are called to check it out. If you can look directly inside your tank to determine your liquid level, this can help guide you to calling the right service company.
A bad smell in the house usually indicates a venting or plumbing issue. If you are not experiencing any backup inside the house or any problems outside the house with the septic system, we recommend you call a plumber.
Depending on the size of tank and number of the home’s occupants, a septic tank will usually fill back up to its normal liquid level after it has been pumped out within a few days to a week. Once the tank fills back up to its normal liquid level, then effluent begins to enter the absorption area again.
If the septic tank is “overfull” this may be a sign of a larger problem with the system (see picture at right). In this case, pumping out the septic tank will give some temporary relief, but will usually not solve the problem long-term.
If the absorption area isn’t accepting the amount of wastewater your household is introducing to the system, then you may experience the same problem again, which may indicate that your system is in need of repair or replacement.
Download a free copy of Understanding and Maintaining Your Septic System to learn more about septic system maintenance.