Inspection - Reliability
Are Septic System Inspection Reports Reliable?
A passing septic system inspection report cannot be interpreted as a warranty that the septic system will continue to function without problems, for any specific future time period. Septic system inspectors base their opinions on readily visible indicators of septic system failure. Sometimes, a septic system receives a passing report and then fails six months later. Any number of factors could have caused the septic system to fail. Those factors may have been in place for several years before the inspection, but may not have left evidence noticeable to the inspector. Or the cause of failure may be the inapproporiate use of the septic system, after the inspection.
An example might be when strong cleaning chemicals have been sent down the drain. The absence of a scum layer on top of the liquid in the septic tank might indicate that strong chemicals had been used. The use of various cleaning agents (e.g. degreasers) may cause the accumulated scum to break up and flow out to the leach field (possibly plugging it). However, the absence of a scum layer, cannot, by itself, be the basis for the septic system inspector to fail the system. Further investigation would be required to provide conclusive evidence that chemicals were present and that the leach field was near failure. This further investigation is often beyond the scope of a typical septic inspection for a single family residential system. After the failure, it is difficult to ascertain what chemicals were used, the frequency or intensity of use of cleaning compounds, or which owner introduced the chemicals.
Prospective property purchasers, who have received a passing inspection report from the seller, can request that another inspection be conducted by an inspector contracted by themselves, the purchaser. That second inspector may or may not have supplemental observations and might reach different conclusions about the system components. But even this second inspection may not accurately predict the future life expectancy of the septic system. Our regulatory and inspection procedures are not perfect, and even the best professional judgement may be unreliable as a predictor of future septic system performance.
When you look at a home that you are interested in buying, consider having a qualified septic system designer visit the property with you. The septic designer can help you evaluate what you would do if and when the existing drain field fails. The designer can start to identify where can you put a replacement drain field, and how much it might cost. All drain fields fail eventually, and sometimes the best use of your time and resources is to figure out what your options might be when that failure eventually happens.
This brings to mind another form of failure that is common with new septic system owners. Many new owners will often paint the house interior to meet their tastes. Septic systems are very sensitive to paint, see our discussion about paint in septic systems.