Using Rainwater in the Home

Rainwater can be used for any non-potable application including toilets, washing machines and outside use. There is no need to flush toilets with drinking quality water bought from miles away. Collecting rainwater at source can also act as a SuDS (Sustainable Drainage System) to prevent flooding. This has become more prevalent as part of planning applications regarding storm water discharge rates.

It is a simple process where rainwater falling on the roof is collected in standard gutters and downpipes, filtered and stored in a tank. When required the water is pumped back into the home.

Size of the Harvesting Tank

Two important factors are the area of collectable roof and how much rain is likely to fall in that particular part of the country. Our tank size calculator takes into account average rainfall specific to the county. Take a look at the 'tank size calculator' here.

Other considerations include the number of people who will regularly be in the home, the number of toilets and any other applications the water will be used for. The industry standard is to set the capacity for a 21 day supply, as it is assumed that the tank will be replenished within that time.

If combining the benefits of rainwater harvesting with a SuDS option the tank will have extra capacity for storm water. RainActiv is designed to collect the excess and then discharge at a calculated controlled rate.

The ideal is to size the harvesting tank so that the toilets will only require rainwater for flushing. However should there be very low rainfall a mains back up is required.

Direct Feed-The appliances are directly connected to the harvesting tank. When a toilet is flushed a drop in pressure is recognised by the pump and water will flow to it. If back up is required a small amount of mains water will be introduced into the harvesting tank. The system automatically reverts back to rainwater when available.

Gravity Fed-From the underground tank water is pumped up into a header tank once or twice a day. From the secondary tank water flows to the appliances by gravity. This makes the pump operation more efficient rather than running every time a toilet is flushed. The Rain Director System costs about 1p/person/day. In the back-up mode mains water will be introduced into the header tank so again a far more efficient method.It is WRAS approved so is accepted by all water providers.

Cost-Complete domestic systems including tank, filter, mains back-up controls, pump, pipe, labels and delivery to mainland UK addresses cost in the region of £1800-£4000.

In most cases installing a system will not yield a short term return but it will future proofwater supply. As a SuDS solution it is a cost effective method of dealing with roof run off.