How Do Underground Rainwater Harvesting Tanks Work?


Most large-scale commercial and agricultural rainwater harvesting tanks are situated underground, leaving many of their mechanisms a mystery. Safe and efficient harvesting benefits from good maintenance, so here’s a look inside the box.  

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Collect The Water With a Pipe

Pipes are the first phase of any rainwater harvesting system. Their role is to channel the water via the filtration unit and into the collection tank. In some systems, the pipes collect the water from the rainwater downpipes, but the majority are connected to the stormwater drainage system. The most efficient setups utilise a single, large pipe that draws from all water sources, which has the added bonus of requiring just a single filter. As filters are the main component requiring maintenance, careful design can help save time and minimise cost. Always check filters regularly to remove any debris, such as leaves, that may reduce the water flow rate and undermine the efficiency of the system.    

Store The Water In a Tank

The quality of the tank is central to the safety of the water. Even when water is not used for drinking, it can pose significant health hazards if the tank is unhygienic. Rainwater harvesting tanks should, therefore, be made of either high-density polyethylene or glass reinforced plastic (GRP). Both materials are durable and have surfaces that resist bacterial contamination. They are also very easy to clean, which is an essential element of water tank health and safety. Tanks are usually embedded in stone or concrete casings and are located 1.2 metres underground, with maintenance access provided by a hatch. The positioning of the tank helps to keep it cool and away from sunlight, both of which can reduce water quality and damage the tank.  

Control With a Power Supply

The power supply and control box are the main user interface for the system. Located above ground in a utility room or similar structure, the control box connects to wires and sensors that control the pump and float switch. Advanced rainwater harvesting systems integrate diagnostic software to troubleshoot any problems and offer feedback on critical functions and maintenance requirements. As storing rainwater underground usually requires the use of pumps to move the water, a good control unit can help reduce maintenance costs by identifying issues before they become serious, and can also ensure maximum system efficiency.  

What Next?

As the world meets the challenge of the climate crisis, rainwater is recognised as being one of our most valuable resources. Collecting and storing rainwater can be an effective way to reduce mains water demand in a way that is safe and cost-effective, but only when the system combines the correct design and materials. To learn more about what’s involved in safely and efficiently harvesting rainwater from your business, please get in touch with one of our fluid management specialists.  

How Much Do You Really Know About Tank Maintenance? - LARGE

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