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.