Harvesting of rainwater is the collection of water for domestic or commercial use that would otherwise go down the drain. Various techniques have been practised for thousands of years to collect and store water, especially in areas of low rainfall. Today, rainwater harvesting systems can be installed in both new and existing buildings and can range from a quick, cheap water butt to a more complex system. Rainwater can be used for the garden, washing the car, showering, flushing the toilet, the washing machine, and even drinking if treated with UV light.
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In a typical rainwater system water is collected from the roof and taken via pipes to a storage tank. A filter removes leaves and other debris and a settlement tank allows small particles to sink to the bottom; floating debris is skimmed off the surface via an overflow pipe, and clean water extracted from just below the surface. Water can be pumped directly from the tank to appliances or to your loft header tank. A float switch in the tank will automatically top up with mains water if the level is too low.
Rainwater collection removes the need for the energy and chemicals used to produce pure drinking water - unnecessary if all we’re going to do is clean the car with it or flush it down the toilet, it also reduces the need for the pumping of mains water, and the energy use, pollution and CO2 emissions that go with it
It reduces demand on rivers and groundwater: the WWF recently reported that over-extraction by water companies is damaging Britain’s wetlands and trout rivers. The problem is most acute in the south-east, where population is increasing and millions more houses will soon be built. 86% of an average household’s water needs can be met by collecting rainwater, without further purification (33% for washing, 25% for toilet flushing, 22% for car washing and 6% for the garden).
Rainwater is soft, and leaves no lime scale; washing clothes in soft water requires less detergent and so reduces water pollution from these compounds; plants love rainwater; it doesn’t contain chlorine, which is thought to be carcinogenic; large-scale collection of rainwater can reduce run-off and therefore the risk of flooding.
Maybe rainwater harvesting is something you want to do regardless of length of payback time, but in certain circumstances, it could be quite a cost-effective thing to do. If you can house a 1.5m³ storage tank in a garage or cellar, you won’t need a submersible pump. Otherwise your tank will be underground and costs will vary for the system and installation.
Some routine maintenance is required, such as cleaning the filters three times a year, keeping gutters clear, and checking everything once a year to see if it is working properly. Decide if you want the water from your tank to be pumped to your loft tank or direct to your appliances (cheaper) – seek advice from suppliers / installers. One such company is Polypipe.
Climate change and population growth mean more people than ever in the UK are living under extreme water stress, with reserves in some areas of the South East even lower than in parts of southern Europe.
Rainwatersystems, with facilitation of re-use are a way of easing this stress, and are an integral part of assessments and regulations such as BREEAM, the Code for Sustainable Homes and the Building Regulations Approved Document Part H.
With a number of domestic and commercial solutions in Polypipes Rainstream RXL range, Polypipe can advise on the design and installation of water re-use system that can cut mains water consumption by up to 50%.