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Tips for installing your septic tank or cesspool

Before installing your tank:

  • Ensure you have appropriate Building Regulation approval in place
  • Ensure you have conducted a percolation (soil porosity) test and that ground porosity is suitable
  • Inspect the tank for any damage prior to installation. Tanks that we supply have been fully tested before dispatch from the factory, and once installed, the manufacturer cannot accept claims for damage
  • Check that you have the correct invert drain depth (neck height) of the tank – a label on the vessel/paperwork indicates the maximum permissible depth
  • Ensure a desludging tanker will be able to access the tank in the future
  • Check the orientation and heights of the inlets and outlets
  • Check that the tank is suitable for its application – septic tanks and cesspools should not be used for silage effluent, chemical toilet waste or any other chemicals

During installation:

  • Use the correct backfill material – some vessels specify that they can be backfilled with pea gravel/pea shingle in appropriate ground conditions. At Direct Drainage, our engineers always backfill with concrete for stability and to protect the vessel and connecting drainage from movement out of the ground
  • Site the tank at the furthest practical location from habitable dwellings. Most building regulations recommend a minimum of 15 metres, whereas some require a distance of 25 metres.
  • Fit the correct cover and frame for the tank, and ensure it is adequate for the site (standard cover for pedestrian duty, or heavy duty if large vehicles will be travelling over the site). Make sure the cover is securely fitted and cannot be removed without the appropriate lifting keys.
  • Consider any ventilation arrangements to avoid foul odours
  • Consider drainage falls, generally 1 in 60/70 between the house and tank, and maximum 1 in 200 for the irrigation system
  • Lift the tank using ropes or slings through both of the shackles fitted on either side of the neck

Do Not:

  • Subject the tank to impact or contact with sharp edges – this can easily damage the structure of the tank
  • Add extra neck extensions to the tank, or build a brick manhole above the tank neck (as this increases the burial depth of the tank). We do not recommend extending the neck of the tank under any circumstances
  • Install the tank deeper than the depth that the fitted neck will allow
  • Install in trafficked areas without a suitable backfill design
  • Site the tank so that it is subjected to excess ground pressure or applied loads, such as may be generated by the proximity of vehicular traffic
  • Lift using only one of the shackles
  • Fill an unsupported tank