Photograph of a swimming pool installed too close to a septic drainfield - in failure (C) Daniel FriedmanRecommended Distance Between Septic System & Swimming Pool

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Septic tank or field clearance distances to swim pools: this document, which discusses distances that should be observed between a swimming pool installation and septic fields or septic tanks is a supplement to our chapter SEPTIC CLEARANCES which provides typical septic tank and field clearances. In this file a detailed septic distances table describes distance requirements between septic components (septic tank, leach field, cesspools, drywells) and other site features such as wells, water supply piping, streams, trees, property boundaries, lakes, etc.

Also see Well Clearances for required distances between wells and septic systems and other site features. In general, septic effluent must be disposed of on the property from which it originates. However more strict clearances and distances than this are required between various onsite wastewater treatment system components and buildings, property boundaries, lakes, streams, wells, and so on, as detailed in the table below. Contact us with corrections or additions to this data.

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Advice on Locating a Swimming Pool Near Septic System Components

Sketch of common septic system component setbacks and clearances.Few septic authorities or codes specifically address the distance that should be maintained between a swimming pool and septic system components like septic tanks, drainfields, or septic mound systems. But we have observed some serious problems when swimming pools were installed near or on top of septic system components.

Problems caused by a swimming pool on top of or too close to a septic field include damage to the drainfield, reduced ability of the drainfield to absorb effluent, redirecting water onto and thus flooding the drainfield, and even causing drainfield effluent to leak out to the ground surface around the swimming pool. This article discusses some of things you should consider when installing a swimming pool near a septic system.

Other than a fifteen foot clearance specified between a swimming pool and septic components for the state of Missouri, and a 100 ft. clearance specified between a swimming pool and a septic lagoon (an entirely different situation), we don't have much guidance in locating swimming pools near septic components. I don-t know an official answer to this question, but here are some considerations when planning to add a swimming pool to a property with a septic system:

  • Avoid septic damage from pool construction process: The distance from mound to pool must be great enough to assure that any equipment used to build the pool, say excavating machines or trucks delivering materials, do not pass on the mound or other septic components - vehicle traffic may cause costly damage if it occurs.
  • Avoid a pool excavation which redirects ground water or septic effluent: If the pool is a below-ground installation, it needs to be far enough away that the hole created by the pool does not interfere with mound operation, say by creating a path for effluent to pass improperly from the mound to the pool excavation.
  • Avoid an above ground pool which directs surface runoff onto a septic field: If the pool is above ground, it needs to be constructed so as to not direct surface or subsurface runoff towards the mound where it could cause flooding of the septic field, and located so that it will not trap surface runoff or pool discharge against the mound. If an above ground pool is "up hill" from the mound it probably should be more distant from the mound than if it were downhill. An In-ground pool should probably be more distant from the mound than an above-ground system regardless of location.
  • Do not empty swimming pools or backwash pool filters onto a septic drainfield: The pool drainage and/or filter backwash also need to be directed away from the septic system.
  • Never put a pool on top of a drainfield or mound: Never locate a swimming pool on top of a drainfield or mound: the work of installation is likely to damage the drainfield, and even a simple, lightweight plastic swimming pool liner and above ground frame, built by tiptoeing onto the drainfield, is still a problem: the impervious area created atop the ground where such a pool were placed prevents transpiration/evaporation of septic effluent, and is likely to also reduce the oxygen level in the soil. Oxygen is needed by some of the bacteria we expect to help break down pathogens in septic effluent.

After also addressing the above considerations, locate a pool 25- or more from the nearest portion of the mound. That should give good working distance for installation and if surface drainage corrections are needed between pool and mound there should be ample room to install such.


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