Topping up rainwater harvesting systems

Posted on 10th May 2019 at 7:21am

Rainwater recycling systems are often designed for use with an irrigation system. However, what happens when we have a dry spell and you need the irrigation system most? The water runs out!

To overcome this, a mains water top-up system can be used. This adds a pre-set amount of water into the storage tank when the water level is low – generally just enough to give one day’s irrigation. Then, if it rains, there is still plenty of room in the tank to catch the rainwater.

The Water Regulations, which is the legal framework for the use of mains water in the UK, are very strict about ensuring the public drinking water supply is not contaminated by rainwater. Therefore, it is not possible to simply connect the water supply to the tank – there must be a physical air break between the rainwater tank and the public mains. An air gap can either be achieved by an air gap in an above ground tank or via a tundish assembly that allows the water to fall into an underground tank by gravity.

Underground tanks must also have an alarm system installed to warn of an overflow situation. This is to prevent the mains water that is being added to the tank flowing down the drain and being wasted.

Access Irrigation manufacture two types of mains water top-up system, one for above ground use and one for below ground use. Each has a level sensor that can be set to trigger the top-up when the tank level falls below a pre-set amount.

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