Site Prep Information

Installation and Tank Base Preparation Requirements
There is no substitute for correct site preparation. Correct site preparation is essential to ensure a long and trouble-free life for your water tank.

It is essential to have your water tank on a FLAT LEVEL COMPACTED BASE. The base of your water tank must be fully supported at all times.

Concrete Slab
Concrete Slab must be at least 25mpa and 100mm (4”) thick with F62 mesh halfway through the mix. It should be screeded flat and level with no high or low spots. The finished surface should have a trowelled finish.

Crusher Dust
Crusher dust bases must be 300mm (12”) wider than diameter of the water tank and prepared as follows:

  • Remove at least 100mm (4”) of natural earth, ensuring the base is flat and level.
  • Refill with at least 75mm (3”) of crusher dust thoroughly mixed with dry cement powder (for a 4m (13’) base we suggest 2-3 bags of cement powder).
  • Once spread, thoroughly compact the crusher dust with suitable compacting equipment, not by any other
  • Thoroughly screed the surface and ensure the finished surface is perfectly FLAT AND LEVEL and free of stones, tree roots, etc. Do not water to set the cement powder, natural moisture will do this when your tank is in position.

Note: Sand is not acceptable.

Molasses Tanks
Molasses tanks must have a concrete slab or suitably constructed tank stand with flat level deck to be considered for warranty.

Inspect the Base Regularly – checking for, and rectifying, any undermining by water run-off or animals borrowing such as toads, mice etc.

National Poly Industries accepts no responsibility for negligence or otherwise, for loss or damage to poly water tanks installed by the customer notwithstanding that the customer has relied upon and followed the recommendations contained herein. These recommendations are a guide only and we do not warrant that the recommendations are accurate or suitable for use by any particular customer or for any particular poly tank sold.

Burying Poly Rainwater Tanks (guide only)

  • As a guide only we recommend that you do not bury your tank anymore than 1 metre into the ground.
  • You must dig your hole 300mm (12”) wider than the base diameter of your tank. If two tanks are to be buried side by side then separate holes must be dug.
  • Prepare tank base as per our INSTALLATION AND TANK BASE PREPARATION REQUIREMENTS (attached).
  •  Completely fill tank with water first then backfill the hole with compacted cracker dust and cement powder. Compact 75-100mm (3-4”) at a time. We also suggest that you erect a fence for safety reasons around the tank. Backfill Ratio = 3 parts cracker dust to 1 part cement powder

NOTE: The above instructions are a guide only. We advise that you seek an Engineers advice for your particular situation before attempting any of the above. Incorrect installation will result in Warranties being made void.