The underground tank is buried up to 1.2 metres under the ground and encased in either compacted stone or concrete. The tank is accessed from the ground via an inspection cover for maintenance purposes, though in most cases, once an underground tank is installed it needs very little human interference. The tank incorporates the following important components:
- Calmed Inlet pipe: This pipe reaches to the bottom of the tank where it terminates in a special flow calming diffuser. This calms the flow of water as it enters the tank and also helps to oxygenate that water as is does so.
- Overflow pipe: An overflow unit incorporates a water trap and a non-return valve that prevents the tank from flooding in the event of backflow from the drain. The overflow pipe should connect to a storm drain or soakaway.
- Float switch: Allows users to monitor the water level in the tank and prevent it running dry. There is usually an emergency water mains inlet that is triggered when the tank water drops below a certain level. a
- Pump: A pump is submerged in the tank that feeds water into the outlet pipe on demand for use in domestic systems.
- Outlet pipe: A pressurised pipe from the pump that conveys water in a regulated flow to the property. This links the underground tank via a network of pipes to water-using systems on the property, such as external taps, washing machines, toilets etc.
The power supply is located above ground typically within a utility room or similar, with wires and sensors connecting it to the pump and float switch. There is also normally a user control interface that allows operators to shut down the system for maintenance and to identify / diagnose any faults.
Underground systems can be used to feed water to almost any domestic property, and are most commonly used for supply the house with water for toilets, laundry and outside use, though are also often used solely for garden purposes. They can connected up to sprinklers and external taps, eliminating the need for the user to access mains water to maintain their garden. This brings cumulative cost savings for the property owner, especially in houses with large gardens, as well as reducing pressure on the local water mains.