Time for the truth
Everyone has a septic fantasy. Whether we like to believe that adding additives or chemical will prolong the life of your septic tank or that it never needs to be pumped. But here are the facts:
1) A septic tank needs to be pumped out when the sludge matter is so much that the septic tank cannot perform as it should mechanically. In a normal working conventional septic tank there is a combination of wasterwater, watery sewage effluent, and a floating scum layer. There should always be enough room (in volume) for the wastewater and the solids to separate properly before the wastewater gets discharged into the drainfield. A septic pump-out is needed when the thickness of the floating scum layer and settled sludge layer occupy so much of the tank volume that the free liquid area is "too small" - the "net free area" has become so small that the "effluent retenetion time", the time that wastewater has in the tank to allow for solids and floating scum to separate from effluent being discharged to the drainfield is too short.
As a rule you should pump out your tank if any of the following are true
a) Total depth of the sludge plus the scum equal 1/3 of the depth of the tank.
b) Bottom of the septic tank baffle outlet has less than 3" of clearance from the bottom of the floating scum layer.
c) Bottom of the outlet baffle is less than 6" from the top of the sludge layer on the septic tank bottom.
2) Additives and chemicals will never extend the life of health of your septic tank. Your septic tank if designed to work, naturally. Additives or chemicals often do more damage than good when it comes to a septic tank. Do not waste your money on these. If you sense issues, beyond a clog, with your tank call for an inspection.
3) "Your tank will never need a pump out" said no one ever. On average a septic tank should be pumper out every 3-5 years. This varies depending on the size of the house, number of occupants, and the amount of wastewater being produced daily. Failure to maintain your septic tank properly is the number one cause of septic tank failure.
4) You cannot save or restore your septic drainfield by getting a pump out. A drainfield bed that is in failure will take years (5-10 on average) to naturally restore itself .
At Whitewater, we often say "when in doubt pump it out" but in actuality, as a homeowner you should keep records of your last pump out.
Think of a pump out as an oil change for your vehicle. Your vehicle might be running smoothly until everything just stops. Just like an oil change, a pump out, when necessary will cost you far less than repair work.