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Guide for Safely Installing Round Poly Water Tanks: Site Preparation, Tank Delivery and Pipework

Guide for Safely Installing Round Poly Water Tanks - Site Preparation, Tank Delivery and Pipework

All Clark Tanks’ poly tanks exceed the Australian Standard for poly tanks, AS/NZS 4766 Polyethylene storage tanks for water and chemicals, which ensures that a poly tank is capable of containing water, liquids for food and beverage manufacture and chemical solutions at atmospheric pressure.

While our poly tanks are designed and built to be very strong, correct preparation and installation also helps to ensure a long and hassle-free life of your poly water tank. The majority of claims made on poly tanks are due to incorrect installation or misuse and could have been avoided.

This article explores the correct way to install a poly tank, in particular a Clark Tanks’ round poly tanks. This articles serves as a guide only and you should always consult the installation manual included with your tank for the most complete and up-to-date advice.

Site Preparation and Maintenance

Before your tank is delivered, you will need to work out your system to ensure you have adequate piping from your gutters to where your rainwater tank will be, that you have appropriate stormwater drainage, and a solid foundation.

Incorrect bases, or bases that erode away over time, will cause your water tank to become uneven over time. Rainwater tanks are generally tested under normal atmospheric pressure on a flat base. If your base becomes sloped, or unstable, then this can cause your tank to warp or fail.

Slab bases for Clark Tanks’ poly tanks:

  • should be on level ground with 100mm thick of compacted crusher dust (free from soft spots) or 100mm reinforced concrete
  • should be at least 200mm greater than the diameter of the tank (i.e., 100mm greater all around the tank)
  • for tanks greater than 36,000 litres must be:
    • at least 150mm bigger than the base diameter of tank
    • at least 150mm thick with 2 layers of F82 mesh 75mm apart and thickening of 200mm wide and 200mm deep with Y16 reo bar at the bottom of the thickening around the edge of the slab
    • 32 MPa concrete mix
  • should have a retainment around base to prevent erosion.

Tank Delivery

When having a poly water tank delivered, unless you have a crane arranged then you will generally need a sufficient number of people to assist with unloading your tank. As a guide for the number of able men required to lift a poly tank include the driver (based upon Clark Tanks’ tank sizes):

  • 1,000L to 13,600L: 2 men
  • 22,700L: 3 men
  • 23,600L to 31,800L: 4 men
  • 36,300 to 46,800L: 5 men

Cranes often require good access to the site and suitable ground for the legs of the crane to stabilise the truck. To ensure you have no surprises, it is important to discuss your site delivery in advance before your tank is delivered.

Once your poly water tank is delivered it is essential that 2.5cm of water is put into the tank. If water is not available ensure that the tank is tied down to secure it from being blown away and damaged.

Tank Fittings and Pipework

To be functional, your rainwater tank will need several holes cut into it. At a minimum, you will require three holes:

  • Tank Inlet – where rainwater flows into your tank, often a hole in the top of your tank where you place a strainer with a tight seal to keep out mosquitoes and debris.
  • Tank Outlet – located at the bottom of your tank you fit a ball valve which is connected to a flexible rubber hose, which absorbs any shock and movement, that is in turn connected to your pipework.
  • Tank Overflow – at the top of your tank where PVC piping is connected to allow excess rainwater to flow out of your tank, away from your tank base and into stormwater drainage.

Important: Ensure all plumbing from your tank’s outlets are well supported and cannot be knocked. This ensures there is no excess strain on tank fitting and wall.


For other tanks accessories you might wish to install refer to our article, Rainwater Tank Fittings and Accessories.