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How to excavate

Horizontal septic tank-01

  1. Excavate so that the depth provides cover over the top of the tank that is a minimum of 6” and a maximum of 30”. Allow space of 18” to 24” on both sides of the tanks.
  2. Bed the tank in compact sand-minimum 6” in soil terrain and 12” in rock terrain. Ensure the tank is installed at an equal level.
  3. If there is excessive soil movement or if soil is black cotton, it is recommended that a 4” to 6” concrete base (with steel inserts) is made of the diameter of the tank.

Water Tank Connections

  1. Install bulkhead fittings on either side of the manhole or the end rib. Appropriate tools should be used for drilling the holes to install fittings and ensure the tank has ventilation.
  2. All holes made for the fittings should be covered with a suitable sealant
  3. Seal the lid with silicone caulking to make it watertight.
  4. Pipe connections should be at least 18” below ground level.

Backfilling exterior

  1. Keep filling the tank with water as you backfill. The level of backfill and water should be even.
  2. Backfill with 12” layers and compact each one before starting the next one.
  3. Backfill over the top of the tanks should NOT exceed 30”.

Backfill material

  1. Backfill should be a sand/gravel mixture or red soil. Sand/Gravel mixture should be 100% smaller than 11/2” and about 50% smaller than 1/4”.
  2. Ensure all backfill is free from steel, wood, and clay.

IMPORTANT: A Septic tank can weigh up to 200kgs depending on the size. Therefore, take necessary precaution while offloading and placing the tank in the pit to avoid any impact on ground which may cause the tank to crack. A small crane or a forklift may be best suitable for the job.

NOTE: Failure to follow the installation guidelines may cause the tank to bend inwards, resulting in cracks on the tank.