Flat Top Underground Tank

Our 25,000 Litre Flat Top Underground Concrete Tank has been designed to be buried with 300mm of topsoil coverage so your tank doesn't need to cover your back yard, your back yard can cover your tank.  Perfect for small sections or unobstructed views. 

80% of these underground concrete water tanks are installed under flat ground and installation in these cases is pretty easy.  Our underground concrete water tanks can also be installed into a bank but are not meant to be used as a retaining wall.  The main  point is to ensure the bottom half of the concrete tank is buried all the way around to hold the tank in place.  The top half can be exposed one side if it suits.  The top of the tank is designed to hold only 300mm of soil and some foot traffic, it will not hold a bank up.  It is better to bury the tank at the top of the bank not the bottom or bury it at the bottom with a retaining wall to hold the bank off the tank.  Phone Ian on 0800 353 222 if you need more information on the structural strength of our tanks.

Underground Concrete Tank

 For any further information or pricing, phone one of our sales team on

 0800 353 222


We offer a full supply and install service

Single Pour Precast

All Eletank branded tanks are single pour precast which means there are no joins under water in the tank, it is a single piece of concrete which is the best manufacturing process available in New Zealand.

Local Support

Wherever possible we use local contractors for all work onsite, our contacts in the area mean we can respond rapidly when needed.


When any tanks are installed below ground adequate sub drainage MUST be provided to stop tanks rising when empty due to rising water tables.  We can add a flange to the bottom of the tank to help stabilise it if high water tables are expected.

Access must be provided through the top of the buried tanks.

If multiple tanks are installed under ground, coupling together should be done by a registered Plumber or Drainlayer as these connections are prone to failure because of the pressures involved and normal ground compaction / movement. All joints between tanks are to be FLEXIBLE.

If compacting around in-ground tanks, fill tanks first, before compacting starts.

Tanks should not be buried more than the 300mm riser height  without engineering advice

If installing tanks under a floor, the floor must be designed to carry the loading and installation must be supervised by a REGISTERED ENGINEER.