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Below Ground Septic & Water Tank Installation Procedures

1. Excavation
Maximum back fill cover (A) 30"
Minimum backfill cover (A) 6"
Maximum wall allowance (B) 12" / 24"
Bedding (C)
Bedding should be a well compacted sand/gravel mixture: 6" minimum in soil terrain, 12" minimum in rock terrain.

2. Lid and Manhole Extension
For proper fit, install the lid and/or manhole extension before you put water in the tank and backfill.
Please note the direction of flow - the inlet is higher than the outlet.

3. Tee and Gasket Installation
Install neoprene gasket into pre-formed hub area.
Install pipe through the gasket and make the connection to the 4" sanitary tee using a solvent weld cement.
Put tees directly under manway/inspection boss.
If the tanks is equipped with an inspection boss, it can be cut open and a 6" pipe can be placed over the boss and extended to ground level for inspection.

4. Backfilling Exterior and Filling With Water
CAUTION: Start filling the tank with water when you begin to backfill, keeping the water level even with the backfill level as you go.
Backfill with 12" maximum thickness layers of sand or gravel, well compacted.  Always compact ends first.  Tamp & compact backfill under inlet & outlet pipes where applicable.

5. Backfilling Top of Tank
With the tank now filled with water, backfill to the surrounding level.
Maximum of 30".

6. Water Cistern Installation
A. We recommend bulkhead fittings (1-1/4" or smaller) be installed in the two 6" boss's located on the top of the tank, or the end wall (flat) either side of inlet or outlet
B. The cistern must be vented.
C. For water-tight seal, lid must be sealed with silicone caulking.


  • Do not use Chem-Tainer septic design tank for drinking water.
  • Always refill the tank with water following periodic septic pumping.
  • Do not install across path of vehicles or heavy equipment.
  • Do not install tanks in excessive high water table areas.
  • Our septic tanks are designed for underground applications only, DO NOT use as a holding tank (with the exception of the 300 and 500 Gallon spheres).
  • Below ground water tanks may be used as septic holding tanks.
  • Never leave below ground tank empty, septic tanks must always be full, water tanks should not be allowed to be less than 25% of capacity.
  • It is important to contact your local or state sanitarian regarding proper installation of sanitary tee assemblies.

NOTE: Failure to comply with installation procedures and guidelines voids warranty.