Onsite Wastewater Treatment System Inspections Versus Evaluations

Onsite wastewater treatment systems (system) treat wastewater from about 25 percent of the homes in Missouri. Wastewater is treated and recycled usually on the property where it is produced by onsite systems rather than by a central sewer collection and treatment system. At the time of a property sale, a homebuyer or lender may want to know about the condition of the system. If a system has an improper discharge or the soil treatment system fails, untreated o r under-treated wastewater might be exposed on the ground surface. Surfacing wastewater or a contaminated water supply could be a health hazard for the home’s occupants and/or neighbors, and if repairs are needed for a failed or inadequate system, they can be costly.

Two types of onsite wastewater treatment systems are commonly used to treat residential wastewater in Missouri. They are sewage tanks with soil treatment systems or lagoons.

Soil treatment systems follow a wastewater pretreatment component such as a septic tank or aerated treatment unit (ATU). Final treatment and dispersal is through lateral trenches in the soil. In septic tank systems, most of the wastewater treatment is provided by the soil. Soil or space limitations sometimes make it necessary to use an ATU or a more advanced system. These systems include components such as filters, pumps, electric controls, distribution valves and media-filters. If a system is properly sized, located, installed, operated and maintained, it can adequately treat waste water indefinitely.

Lagoons are above ground pond-like structures that are used to treat wastewater from a single-family residence. Air, sunlight and long retention time aid in this method of wastewater treatment. Any overflow from a lagoon must soak into the soil, staying on the property where the lagoon is located.

It is often difficult for the property owner, buyer, or lender to know the condition of an existing system since most components are underground. For the most part, local public health agencies no longer inspect existing systems related to real estate transfer. The help of a licensed inspector can be obtained to check the condition of the system. Individuals must be licensed by the Missouri Department of Health and Senior Services to perform private assessments of existing systems for real estate transactions. There are two distinct types of assessments performed by these licensed individuals: inspections and evaluations.

An inspection provides a thorough assessment of the condition of a system and all components. In addition, a hydraulic test is conducted to determine whether a soil treatment system can accept normal anticipated wastewater flows. An evaluation reports on the functionality of the tank component(s), observable condition of the soil treatment system and any signs of past or present system failures. A hydraulic test is not performed during this type of assessment. Therefore, the soil treatment area is not tested. A report showing the results of either assessment is provided to the person who requested it. Copies are also provided to Department of Health and Senior Services’ Onsite Wastewater Program staff and the local onsite wastewater agency. See Training Manual for Private Inspection/Evaluation Assessment for more detail regarding inspection and evaluation protocols.

The table below will help you compare the difference between an inspection and an evaluation. When applying for a home loan, check with the lender to determine which type of assessment is required, if any.

When you have received an assessment report, it is important to understand what it means. An assessment report might alert the property owner, buyer or lender to critical items or potential deficiencies with the system. If there are deficiencies, the parties involved in a real estate transaction must decide what system repairs will be made. State regulations do not require systems to be brought up to current standards as a result of an inspection/evaluation to be sold. However, in some cases, local standards are more stringent than the state regulation.

Some deficiencies noted on an assessment report are an indication that the system has failed in the past or could potentially fail soon. Failing systems can be a health hazard for the family or guests in the home and others in the neighborhood. Also, if the local authority receives a complaint about a system that is creating a nuisance, the property owner may be required to make repairs. Examples of nuisances are wastewater from a soil treatment system surfacing on top of the ground, or wastewater draining onto someone else’s property, or into a stream or lake.

Other reported deficiencies could indicate that components of the system do not meet current standards or that routine maintenance has been neglected. For some of these systems, proper maintenance and system management could extend the potential useful life of the system.

Both inspections and evaluations provide an assessment of the water supply if it is from a private source. A water sample that shows bacterial contamination is reason for concern whether the contamination is from an onsite system or not. An inspector can resample the water after the water system has been disinfected. Two good samples, at least one week apart from each other after chorine has been flushed from the system would show that the drinking water system is safe, but regular sampling is recommended. Additional bad samples can be further investigated with the assistance of a licensed well driller or experienced plumber.

If repairs to the system is planned, contact the local administrative authority regarding permit application requirements before any construction or major repair. The repair/installation must comply with current standards.

Comparison of Inspections and Evaluations