Mound Septic Systems

Usually, a mound septic system is used when the soil isn't conducive to treating wastewater. Water from waste has to go through at least three feet of dry soil in order for it to be treated as it needs to be. For people that live in an area that has a water table that is high or soil that doesn't drain properly, they must actually bring sand into the area and then the drain field is built on top. This is known as a mound septic system.

There are many configuations that mound systems are designed in, but a straigh line of about 30-60 feet long is most common. Sometimes you see a design that looks like a double H. This is the pattern that the pipes are placed in, and have 1/4" holes along with a diameter that is usually one and one half inches.

A simple schematic diagram of a typical mound septic system.
(Converse & Tyler 1990)

There are two different tanks that are employed in a mound septic system. The primary tank is used to allow the solids to settle, and the other one features a pump that comes on at a specific water level so that the wastewater can be pushed out to the mound. The pressure allows the wastewater to be evenly distributed within the mound.

If you live in an area that has soil that is full of rocks, a mound septic system can also be used since the wastewater will go through it without the need for treatment. A mound septic system can also be used if you suffer from soil that percolates water too slowly, since much of the wastewater goes back into the atmosphere due to evaporation. Some of the potential drawbacks to using a mound septic system are:

1. They are very expensive since they need the use of specialized equipment as well as more manual hand shoveling, and the entire process is extremely involved, unlike a traditional septic system.
2. Most people find that they are grossly unattractive. This is because lots of people don't relish looking at a huge hill of dirt in their yard every day. On the other hand, people are now discovering ways in which to landscape their mound septic systems enabling them to appear quite lovely.
3. They are subject to problems more often that an ordinary septic system. Some of the primary reasons for a mound septic system failure are:

Solids become trapped in the wastewater- Usually, pumps burnout and pipes clog due to solids in the wastewater. The pump impellers are harmed and the holes in the pipes become clogged. This also plugs up many of the pores in the soil, so it is absolutely necessary to always use the right types of wastewater filters, both in the tank and also the washing machine, to be certain these solids do not have a chance to clog the pipes.

Too much water in the system- Mound septic systems are sized with plenty of cushion in the event of a disaster, but if pipes leak, the system can be overwhelmed in only a few days, so it is imperative to be certain there are is no leaky plumbing, like a toilet that keeps running.

Chemicals that kill off natural bacteria that assist in solids consumption- The natural bacteria found in the tank are what helps clear the wastewater of solids, and when too many chemicals are used, these bacteria are destroyed. Using chemicals on occasion is fine, but don't make it a regular occurance.

The use of a mound septic system has its good points and bad, and it is up to the homeowner and the building department to decide which option is the best for their situation. Start with a certified soil test to get an idea which kind of septic system will be best for your building project.