Some people, when they buy or have a water tank installed would like to bury their tank, this can be done to reduce the height of the tank – especially if it is blocking the view, or to hide it away completely. Steel tanks will corrode if buried, so, for that reason, they are best left above ground, however concrete in ground water tanks can be buried, as can poly water tanks.
When it comes to poly tanks it’s important that you just don’t bury *any* poly tank. Those standard *above ground* tanks have not been designed to withstand the pressures of the earth and if they are not properly supported they can collapse due to the outside pressure. Having said that you can partially bury a poly water tank.
Before you start burying an in-ground water tank it’s important to get the advice of an engineer as the desired depth, type of soils and the location needs to be evaluated by an expert before partially burying your tank. This is to ensure foundations are not eroded and your tank will be properly supported.
It’s best not to bury a poly tank more than 1 metre into the ground and your hole should be 300mm or 12 inches wider than the diameter of the base of your water tank. If you plan to bury two tanks you need to dig two separate holes. You must prepare the foundations for your tank as normal, that is it must still sit on a compact, level and flat base. Bases can include concrete, brick, gravel or solid dolomite between 300mm and 400mm deep.
Ensure that the surrounding soil left in the walls of the hole are solid if there is any major water seepage into the hole from the surrounding soil the site will not be suitable
Once the tank has been placed on the base, fill your tank with water then backfill the hole with cement powder and crusher dust compact just 75 to 100mm at a time.
It’s important that tanks be buried into the ground only half way up its wall height and that your outlet that picks up from the tank comes through the tank roof, or alternate plumbing from the base outlet is needed. If there are 2 x 90mm inlets coming into the tank, you will need at least 2 x 90mm overflow pipes. Overflow must be piped away from the tank
You can bury your poly tank completely – you just have to buy a tank that has been designed to be an in-ground water tank. In-ground tanks are designed to provide you with a wholly hidden water storage solution, they are suitable for installation under a driveway, pathway or garden.