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Coronavirus (Covid-19): service updates, support and health advice.

Septic tanks

A septic tank stores sewage sludge for long enough, and in the right conditions, for it to partially break down (anaerobic decomposition). It is normally a two- or three-chamber system. It creates an effluent discharge. Please consult the Environment Agency for more information.

  •  It is important to note that you must not let effluent from a septic tank discharge into a watercourse
  • You may let effluent from a septic tank soak into the ground, provided that it does not create a pollution risk to surface streams or groundwater resources (underground water)
  • You must carry out a percolation test before allowing effluent to soak into the ground. This establishes whether the land is suitable. Areas of heavy clay or steeply sloping sites are not normally suitable. The capacity of a septic tank should be calculated using the following formula: C = (180P + 2000) where C = capacity of the tank in litres and P = population served
  • A septic tank should be desludged and serviced at least every 12 months. Emptying services can be found in the local phone book (you are advised to get several quotes as prices can vary considerably)
  • The septic tank and soakaway area should be sited not less than 10 metres from any ditch, drain or watercourse. Soakaway pipes should be placed as low as possible, usually within 1 metre of the ground surface
  • It is best to place a septic tank and soakaway at least 15 metres from any dwelling.
  • You may need permission from the Environment Agency for the discharge into the ground. Please see the consent requirements for more information
  • You must not install a septic tank or soakaway near any well or borehole. The minimum distance required will depend on specific site conditions
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