Water Tank Pad Preparation Guide
What base do you need for your water tank?
There are several types of base that can be used for water tanks. Depending on the type and size of your tank, the options can vary.
The below table shows the tank pad options for each type of water tank.
| Base type | Slimline Tank |
Round tank (up to 21000L) |
Round tanks over 21000L |
Fire Protection /Commercial Tanks |
|---|---|---|---|---|
| Compacted Base | ||||
| Crusher Dust | ||||
| Concrete Pavers | ||||
| Concrete Slab |
Compacted Base
For large round tanks, especially in rural settings, a compacted base is the most common type of tank pad.
See our guides linked below to provide to your earthworks contractor to ensure suitable preparation of your compacted base.
Crusher Dust
Requirements:
Pre-Assembled Tanks (up to 21,000L)
For pre-assembled tanks, the pad should be compacted, level and at least 100 mm thick with particles smaller than 3mm diameter. The diameter of the tank pad should be at least 100 mm wider than the tank and have a border of a solid weather resistant material, such as treated pine.
Rural / Large Tanks
For larger tanks assembled onsite (over 21000L), the tank pad must be at least 2m larger than the tank, 75mm thick, with particles 6mm or less. The tank pad should be level to within ±10mm. As the liner of larger tanks will sit against the base, the prepared surface will also need sand or a geotextile layer
To prevent erosion from heavy rain or damage from burrowing animals, a border should be placed surrounding the tank. For the exposed base around the tank, it is recommended to add a coarse aggregate as this will assist in preventing erosion.
Concrete Pad
A concrete pad will provide the best support for all types of tanks, and for some tanks such as fire protection tanks, it is the required base type.
Your concrete pad for tanks up to 21000L should be a minimum of 100mm wider than the edge of the tank and 1M wider than the tank edge for tanks over 21000L.
For installations on sloping terrain, it is recommended to consult with a builder or engineer prior to constructing a concrete tank pad. Also needing to be considered for new slabs is the required curing time prior to installation, for which a minimum of 5 days will be required.
Concrete Paver Pad
Concrete pavers can be used as a base for slimline & round water tanks (up to 21000 litres).
You must prepare an area before laying your pavers; the area must first be cleared, dug down to firm ground and levelled, concrete and sand mix spread out with a minimum thickness of 75mm.
As with a concrete pad, the entire base of the water tank must be supported, and the overall size should be at least 100mm larger than the dimensions of the tank itself.
You can then lay your pavers. There must not be a gap greater than 5mm between each paver. Once laid, ensure you water the area to set the concrete (ensure your hose is on the spray function as the jet function will dislodge the concrete and sand). You may place your tank on the pad at this stage; however, it is recommended that you only fill your tank up to 100mm (roughly two ribs) for a minimum of 48 hours to allow the pavers to settle and set.
Important note on tank pads:
For your warranty to be valid, your tank pad must meet the minimum requirements for your tank type and application.
Damage to your water tank due to a tank pad being constructed below minimum requirements can be costly, so please contact us with any questions to ensure you have the best installation and peace of mind of your warranty coverage.
Things to Consider
1. Water tanks require a level base. Sloping pads will void your warranty. Water will travel to the lowest point which increases pressure on a single point. Eventually, this can result in the failure of your tank’s structure.
2. All sections of the water tank must be fully supported. The weight of the water will concentrate in unsupported areas of the tank, pull the base away from the wall, and destroy your seal. Damage can vary from a small leak to structural damage that may be unrepairable.
3. Where crusher dust or sand are used for the tank base, particles should be smaller than 3mm for preassembled tanks and 6mm for tanks assembled on-site (rural tanks). This is to reduce the risk of damage to the tank base or liner.