Understanding Septic System Maintenance Principles

Understanding design and maintenance principles will help ensure the highest functioning and longest-lasting onsite system goes in the ground.

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This is the last in a series of stories highlighting design principles that will help properly maintained onsite systems last indefinitely.

Knowing the type of soil at a system installation site is an absolute must. We are always nervous when we hear statements like: “I do not need to know soils; I just need to be able to follow the plan from the designer.” These comments usually come in situations where the designer and the site evaluator are different people. Upon further questioning, we typically find the site evaluator gives the information to the designer and the designer has never visited the site. This can lead to a misinterpretation of the soil information, and consequently to a bad design decision. In fact, the majority of the design mistakes we see involve the initial interpretation of soil characteristics.

There are tools to help with soil decisions, but there is no substitute for being on the site and observing the soil and landscape characteristics. Useful site information can be obtained through the web soil survey. The National Resources Conservation Service website provides information on soil characteristics for a given area. This is good preliminary knowledge to have before any borings or pits are opened to investigate the soil characteristics. This can help identify features that may be encountered at the installation site.

IDENTIFYING FEATURES

Features any site evaluator, installer and designer should be able to identify are soil structure, texture and color as it relates to saturated soil conditions, as well as the presence of dense or other limiting conditions. Installers are the last line of defense in the process; so if you see something that doesn’t conform to the evaluation when excavating for sewage tanks, supply lines, etc., it’s time to go back to the designer/site evaluator to see if this impacts the design.

There are three parts to knowing the delivery. The first is how the sewage moves from the house to the septic tank. Is there enough fall so this can be done by gravity or will a sewage ejector pump be needed to lift the sewage up from the basement or lower level? This can have an impact on the necessary tank capacity.

Second, where does the effluent go next? Is more treatment necessary, or is the effluent simply moved to the soil treatment part of the system? Is a pump necessary to move the effluent to any additional components? If effluent is moved by gravity, again, is there enough fall available while maintaining the required separation distances? Will effluent be pumped to a pressure distribution system or to a gravity-fed series of trenches? Answers to these questions will have a bearing on the size of the pump if one is needed.

Third, how is the effluent distributed to the soil for infiltration? If by pressure or gravity, there will be specific piping and placement requirements.

In all three of these areas, specific sizes, strengths and types of piping will be required. The design will specify how the pipes are handled and laid, as well as proper bedding materials for the project.

CONSIDER LONGEVITY

If we expect our systems to last indefinitely with proper care, we need to factor that longevity into the design and installation from the start. The designer and installer need to know and understand the unique maintenance requirements of the technology used. Systems need to be designed with convenient maintenance in mind. System components must be accessible.

Examples are risers to the surface so tanks can be accessed and cleaned at regular intervals; clean-outs provided outside the house in the house sewer line; pumps easily accessible for removal and repair – installed with quick-disconnect fittings to allow removal without taking the floats out at the same time. For media filters and ATUs, both the designer and installer need to be aware of the maintenance requirements. In some cases regular testing of the effluent will be required.

Both professionals should know expected frequencies of maintenance for the different technologies. For example, pressure distribution laterals with 1/4-inch diameter perforations are cleaned every three years while ones with smaller perforations are cleaned every year.

Finally, the homeowners need to be a part of this discussion. Provide them with maintenance requirements specific to their system. Explain how and when it should be performed and outline the associated costs involved with caring for the system. We have long been supporters of providing homeowners with an operation manual specific to their system.

There is so much more we could talk about relative to design and we will revisit design-specific issues in the future. 



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