Septic System Basics

All modern homes built in the United States have some system for disposing of effluent (AKA “Poop”) from the house. In most suburban areas, effluent is directed from the house to a piping system that leads to a city sewer. In more rural areas, homes have an Onsite Sewage System (OSS). That is individual systems that serve one or a few homes tied into it.

If you are replacing a mobile or manufactured home with a stick-built home, this is an advantage to you as the septic will already be at the site. It may need to be re-certified or in some cases retrofitted, but it almost always cuts down on certain site development costs as well as time in permitting.

The Scoop On The Poop

The type of system that a septic designer will recommend for your site depends on such factors as what type of soil you have, slope of the land and so on.

There are basically two types of systems:

1. Gravity OSS: Gravity systems are typically the most desirable, simplest, and least expensive systems you can get. This system utilizes gravity to move the effluent. Due to the nature of some soil types and sites in Washington State, however, they are not always possible. True Built Homes are designed with this system in mind normally.

2. Alternative OSS: Everything that is not a gravity system falls under this category. These almost always require some form of a pump system to move the effluent from the house to the drain field. It is important that you know that since we normally plan for a gravity system, if you have a pump, running the power to operate this pump is an additional cost. This averages anywhere between $200-$1200 depending on the type of system you require. You can either have your own electrician run this power or if you prefer we will have it done for you.

Here is a brief rundown of the various types of systems:

  • Pressure Distribution System (PDS): Similar to a gravity system, except that it relies on a pump to evenly distribute effluent over a drain field area instead of gravity.
  • Sand Based Treatment System (SBTS): Like the PDS, it uses a pump, however after the pump pushes the effluent through sand for aeration before it reaches the drain field to help in filtration. This system is used for the protection of nearby wells, surface water, or shallow groundwaters.
  • Aerobic Treatment Unit System (ATU): Similar to the sand system but uses a tank where the effluent mixes directly with air to speed up the treatment process before it reaches the drain field.
  • Drip Irrigation Dispersal System (DIDS): Usually used in connection with either SBTS or ATU system. After the filter and pump, the effluent is then dispersed through driplines (similar to those used for plant irrigation) that are laid just below the surface of the ground. Used ideally when the soil is shallow, and/or the drain field is smaller due to site size constraints.
  • Glendon System: A very high level of treatment found often in Kitsap County. Effluent is treated in a containerized septic drain field system before it is dispersed into the surrounding soil. This is one of the more expensive but more effective systems.
  • Mound System: In this case, a mound is built above ground level to become a drain field. Aesthetically this is probably the least desirable system (who wants to look out their window at a waste disposal site?) however it may be necessary under certain site circumstances, such as very dense or compacted soil (clay, bedrock, etc) or a very high water table.

For more general information on septic systems see the EPA’s “A Homeowners Guide to Septic Systems”

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