There are two general rules to follow when it comes to preparing a base for your rainwater tank:

  1. ALL rainwater tanks need to be installed upon a solid and flat base. You should consult the manual of your tank manufacturer for exact specifications, however tank stands, concrete pavers, concrete slabs and compacted crusher dust are some common foundation types for both AQUAPLATE® steel and poly tanks.
  2. Tank base should be wider than tank for adequate support. Again, consult your tank manufacturer, but generally 100mm longer and wider than your tank is the recommendation.

Base Preparation for Poly or Steel Water Tanks

Click the relevant tank material below for detailed base preparation instructions.

ThinTanks Note: ThinTanks poly tanks have specific install instructions. If purchasing a ThinTank, please refer to the 1000L ThinTank Guide or 2000L ThinTank Guide as appropriate to your needs.

If you need to prepare a base for your QTank poly tank, it’s best to do it before your tank is delivered.

You can easily construct a base of your tank out of concrete, pavers, or compacted gravel, crusher dust or packing sand. You could also buy or build a tank stand.


  • Keep in mind the height of the tank – if you don’t have enough clearance under the downpipe/s or eaves, you may need to construct your slab further away.
  • If positioning the base against a wall of your house, include a very small slope away from the wall in the base so rainwater that falls on it will naturally flow away and not
    pool against the house.
  • Check that no tree roots or other sharp objects are in the area which could break through the bottom of the tank.
  • The water inside your tank weight approximately 1kg per litre – your tank’s base must be able to support the weight of your tank when full.

Concrete Base

  • An ideal thickness of a concrete base is 10cm.
  • When boxing up your base, make sure the base is up to 100mm wider than the tank.
  • Use reinforcing mesh placed in the concrete to provide extra strength.
  • The base will need approximately seven days to fully harden before placing a tank on it.

Crusher Dust Base

  • Please note – this isn’t preferable if the land the base will be on is not naturally flat.
  • A compacted base should be about 30cm wider than the tank.
  • Consider excavating the site of the base so when the material is laid down, it is the same height as the surrounding ground level.
  • To make the base more stable and keep the materials in place, first lay down a boundary of pavers or wood (pine sleepers) – you could also use the edge of a concrete pathway as part of the boundary if available.
  • Compact the materials to enhance their stability.

Tank Stand

  • Stands should be constructed with hardwood decking with gaps between the boards 25mm (1”) or less.
  • Ensure the stand’s structure can support the weight of the tank when full.

This brief guide for base preparation should be followed to ensure a correct foundation is laid for your AQUAPLATE® tank. Damage to your tank due to failure or movement of the tank base is not covered by the warranty. Please keep in mind that 1000L of water weighs 1000kg, and this is a significant force. Soft ground may subside under the weight of a full tank.

The base of your tank is made with double sided AQUAPLATE® i.e. the inside and outside of the tank base is coated with a polymer film to prevent corrosion. The tank may be in direct contact with the tank base and the tank will not corrode. Hence there is no reason to elevate the tank above ground level.

This base preparation guide should be taken as a guide only. Specific details on the construction of a tank base should be referred to an engineer for formal advice. Tank Shop and Kingspan accept no responsibility for the failure of a tank base.


Stand construction must be certified as strong enough to support the tank’s weight. Consult a structural engineer to ensure the construction and footing is sufficient for the tank. The top of the stand must be flat, smooth and level. Tank stands may be made with varying leg lengths to accommodate a sloping site. Kingspan Water tank stands are available to suit a range of tanks.

Concrete Paver Base

To use a concrete paver base, the area must be cleared down to firm earth. A paver base installed on soft ground (i.e. a garden bed) will subside over time, and is not advisable. Once dug down to a firm surface, spread sand and cement mix 75mm thick over the entire base, level out then proceed to place concrete pavers flat on top. Once laid, shower the pavers with water to set the sand and cement off. Paver base is to be large enough to support all edges of the tank. Tank may be placed on to paver base straight away. Do not fill tank above 2 corrugations for at least 48 hours.

Concrete Base

A concrete slab base is the most suitable base for your AQUAPLATE® rainwater tank. Construction of a concrete base needs a minimum of 100mm thick concrete and F62 mesh, on a flat level area. If the tank is to be positioned in an area that is on a slope then the thickness of the slab is to be increased and the mesh to be a higher grade. The slab must be flat, smooth and level. Finish with a metal trowel is advisable. Slabs must be large enough to support all edges of the tank, and should be at least 100mm longer and wider than the tank. Slabs must be allowed to cure for at least five days prior to placing tank on slab.

Crusher Dust Base

Crusher dust bases are only suitable for larger diameter round tanks (not small round tanks, square tanks, slimline or modlines). The crusher dust must have no particles larger than 5mm diameter. The crusher dust is to be 100mm thick. It must be compacted, level and flat. A border must be placed around the crusher dust to ensure it does not erode over time or is undermined by heavy rain or burrowing animals. The base should be large enough to support all edges of the tank. Tank may be filled straight away. Coarse aggregate should be spread over any exposed crusher dust, after the tank is positioned, to prevent erosion.

Note: Care must be taken when positioning the tank on a crusher dust base to ensure it does not dig in and create an uneven surface.

Note: Solid tank foundations are extremely important to protect your tank warranty. Keep in mind 1000 litres of water is extremely heavy and weighs 1000 kilograms! Soft ground may subside under the weight of a full tank resulting in a tilted or cracked foundation. All tank manufacturers normally state their warranties are voided if their tank is damaged due to an incorrect or failing base.
Disclaimer: Information on this page is provided as a general guide to help with installing rainwater tanks. Tank Shop and its partners are not liable for any actions you take in relation to the information or instructions on this page. You assume full responsiblity should you choose to proceed with any advice.