Does Placing an Above-Ground Pool on Top of a Septic System Cause Problems?

A septic system allows homes too far away from a municipal sewage plant to process their excess water and waste safely. If you've got a small property with a septic tank, you may be tempted to take advantage of the extra space over the system by installing an above-ground pool, which may lead to serious problems.

It is recommended that you do not drive or park a vehicle over any part of your septic system because the weight of the car leads to compaction and pipe or tank damage, says the Rouge River Watershed Program website. An above-ground pool filled with thousands of gallons of water weighs much more than even large trucks or sedans. Adding all of this weight over the drain field could crush the pipes, or it could crack the concrete of the holding tank if installed over it.

The extreme weight of an above-ground swimming pool also pushes the soil below it very tightly together. This super-compacted soil doesn't allow water and waste to drain out of the holding tank of the septic system properly. Both solid waste and water will build up in the tank. When the tank is completely full, the drains in your home won't flush or empty until you have the tank pumped. You would also have to remove the pool and dig out around the system before it would function properly again.

Accidental spills or splashes from the edges of the above-ground pool damages a nearby septic system, as well. The chlorine used to disinfect pool water and prevent algae growth kills the beneficial bacteria in a septic tank that breaks down waste, according to Inspectapedia. Too much extra water from draining or emptying a pool onto the drain field floods the system, causing clogs from solid waste when it shifts. This also upsets the bacterial balance in the septic system.

Even if you place a very lightweight plastic pool above your drainfield or septic mound, the plastic will prevent the proper evaporation and oxygenation that allows the soil to process waste. While the bacteria that live inside the tank and drainfield are anaerobic and need no oxygen, the bacteria in the soil that do some final processing of the waste do need it. Blocking their air flow makes the ground swampy with contaminated water that poses a serious health risk.