This simple tech can help reduce your reliance on mains water and even reduce flood risk – but is it right for your project, asks Nigel Griffiths

Nigel Griffiths

The Klargester Gamma rainwater harvesting system from Kingspan is a shallow-dig solution, requiring less excavation and less backfill than traditional tank installations. Shown here using a header tank, it can also be supplied as a pumped setup

Put simply, rainwater harvesting is the collection and storage of rain for a variety of uses – but not for drinking. The majority of systems are used to flush WCs, although it’s also possible to supply washing machines (the soft rain is ideal for laundry as it eliminates the need for conditioners), irrigate the garden and for other non-potable purposes.

Harvesting and reusing rainwater reduces your need for water from the mains. This minimises pressure on the conventional supply and, if your property is metered, can cut your bills. Rainwater harvesting also has a beneficial, if minor, effect on the drainage system as it holds run-off when it rains, rather than allowing it to go directly into the drains.

Owing to climate change, spells of heavy precipitation are expected to increase, so widespread harvesting and storage of rainfall could reduce the risk of local flooding. This might be a boon for some planning applications.

In most cases, the primary collection system is the roof. There are two reasons for this: firstly, there will already be a setup in place (the guttering and downpipes) that can be used to convey rainwater to a storage tank. Secondly, although roofs are not perfectly clean, there are fewer contaminants than are present at ground level. Foreign bodies such as leaves, for example, can be easily removed.