Installation Instructions for Polyethylene Underground Tanks

  • The tank is constructed for direct burial, confirm depth of burial before installing.
  • Most poly tanks are approved for two (2) ft. of earth cover. If in doubt contact Canwest
  • LP series & RKP300 & 500, are rated for or up to four (4) ft. of earth cover.
  • Do not locate tank under pathway of vehicles or heavy equipment.
  • Keep tank away from large roots and sharp rocks.
  • Extra caution must be taken in clay, heavy soil or fine sand.
  • If used as holding tank, pump or siphon chamber, ensure that the tank is adequately vented to prevent internal pressure
  • Do not install tank in areas with high water table.


Complete Polyethylene Underground Tank Installation


Read through or download and print the complete installation instructions for polyethylene underground tanks.


Installation Procedures



  • Allow enough clearance around the tank to correctly place the back-fill around the tank.
  • Bedding should be leveled pea gravel, 6” deep, minimum in soil terrain and 12”deep minimum where clay or rock is present.


Placing the Tank

Prior to placing tank, check for shipping damage. Ensure that the tank is firmly embedded in pea gravel and that the tank is level, before starting to backfill. Shape bedding to the contours of the underside of tank to eliminate voids that later can cause settling of the tank



Install manway cap, and cover open pipe connections prior to backfilling.


Caution: Lid must be kept in place during and after installation to avoid possible manway distortion.


Tank must be bedded & back filled with 12" Pea Gravel around the tank.
Back-fill evenly around tank to avoid shifting the tank side to side.
Inlet – outlet must be level end to end, to ensure gravity flow
Shape bedding to the contours of the underside of tank to eliminate voids that can cause settling of the tank and bring it out of position.


Important: Ensure backfill is properly placed around the tank.


During Installation of the Tank

  • Check levelling of tank periodically during backfilling.
  • Backfill and install manway extension (if any) to the surrounding grade level. Refer to drawing.


Pipe Connections

Make solvent weld pipe connections to pre-plumbed tank only when tank is firmly secured and unlikely to shift during remaining backfilling.




These guidelines are set out for proper burial of a polyethylene tank for underground applications, and must always be followed. They are especially important where the soil contains rock or clay. Improper burial may cause damage to the tank and void the warranty.


In case of conditions not covered in this text, or if there are any questions regarding soil or burial method, please contact our factory.

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