Harvesting Rainwater

Harvesting rainwater by collecting water from your roof and using it to flush toilets, wash clothes and provide water for outside taps is really beneficial for the environment.

The majority of UK homes use drinking water for these functions. The process of creating clean drinking water is carbon intensive and unnecessary for these basic household functions.

Kendal resident Robert harvests rainwater for his household of 2. Only a third of the amount of water goes through Robert’s water meter compared to a household that doesn’t harvest rainwater.  As a result the Water Authority doesn’t have to treat and pump the remaining two thirds, enabling the Water Authority to save carbon and the household to save money.  Additionally, harvesting rainwater creates a flood prevention buffer.

Robert has provided the following case studies to illustrate how he integrated Rainwater Harvesting in two houses.

Case Study 1

Fitting a rainwater harvesting system some 15 years ago into a 1930’s semi-detached house.

The retro fitting of a system would at first seem a very difficult task to accomplish.  It wasn’t.  Perhaps it was the layout of the house, which was very standard, but it was achieved quite easily by an ordinary do-it-yourselfer.  The garage had a basement and 2 separate tanks, one capacity 1250 litres (included pumping apparatus) and one capacity 1500 litres, were installed there and the water from the house roof all flowed onto the garage roof and then went internal to the tanks.  The overflow from the tanks was directed back into the drains with a very small amount of underground work.  The system operated perfectly and we only ran out of water once in the height of a summer when the automatic top up from the mains put a small amount into the tank which tied us over until the next rain.  The household was 2 persons and as far as we know the system is still operational.

Case Study 2 (current system)

Fitting a rainwater harvesting system some 6 years ago during the full refurbishment of a property.

Because the property was being totally refurbished, all the house drains taking the water from the downspouts were diverted into an underground tank of 5000 litres which was positioned so that the overflow readily went into the existing top water system.  The system has automatically topped once due to a faulty sensor not a lack of water as 5000 litres seems much more than adequate for a 2-person household.  This system from Rainwater Harvesting Ltd has not been as reliable as the equipment in case study 1 as we are on our 3rd pump, all repaired under the 2-year warranty.

Advantages of one study compared to the other

Study 1:            Filter system (Wisy) much better

Cheaper to install as no big hole to dig for tank

Pump on outside of tank so more friendly operating environment

Study 2:            Neater as tank underground

Easier to do pipework in house as it was being fully refurbished and so replumbed

On both systems the pump senses a drop in pressure in the pipework when a tap is turned on or a toilet is flushed and automatically shuts off when the pipework is back up to pressure.  It is possible to install a header tank and gravity feed everything so keeping the pump switch on/switch off to a minimum.

It must be remembered that if the electricity supply goes off or the pump fails so does the system, so it is necessary to be able to supply the system from the mains on such occasions