The harvesting of rainwater is a relatively simple concept, however the majority of homeowners are unaware of its benefits. Rainwater harvesting is the collection of water that would otherwise have gone down the drainage system, been lost through evaporation or soaked into the ground. Collected rainwater has predominantly been employed for outdoor purposes, however the use of rainwater inside the home is becoming more favourable as water costs increase.
Water is currently metered at between £1-2 per m³ and is expected to steadily increase as prices have already risen by 50 per cent since privatisation. At present, around 25 per cent of UK households are metered but New Legislation brought in this year allows water companies the right to meter all of their customers. With New Legislation, increasing water costs and enforced hosepipe bans, the benefits of harvesting rainwater become apparent.
Rainwater harvesting systems can be installed in both new and existing buildings. Toilets, washing machines and outdoor use account for 50 per cent of domestic water consumption. If correctly harvested and stored, rainwater can be used for all these requirements without further treatment. At present there are no UK regulations concerning rainwater use for toilets, washing machines and gardens, however the back-up from the mains must comply with the Water Supply Regulations 1999. Rainwater can be advantageous for washing purposes as its composition and softness reduces the need for harsh detergents. Rainwater is naturally soft and doesn’t contain the chalk and lime deposits that are found in hard water. It is these mineral deposits which cause the build up of scale and scum around baths and basins.
The minerals contained in hard water settle as a deposit of scale whenever the water is heated or when cold standing water evaporates. Over time, hard water can have a devastating effect on pipe work and can cause premature failure of water heaters. It is estimated that in Germany 100,000 rainwater systems are installed every year and recent trails have shown extended life for washing machines that run on rainwater.
Mains supply water is chemically treated to remove impurities to produce pure drinking water. However, treated water is not needed for any other use apart from human consumption. Rainwater collection removes the need for the energy and chemicals used to produce drinking water which seems unethical to simply flush down the toilet or wash the car with. Studies have proven that rainwater is actually beneficial for the garden and the car as it contains a lower amount of Total Dissolved Solids (TDS) than normal mains water. TDS refers to any amount of cations, anions, minerals, salts or metals dissolved in water. Some dissolved solids are from organic matter such as leaves, pesticides and industrial sewage.
There are also environmental benefits of harvesting rainwater as by utilising rainwater efficiently the demand on rivers and groundwater is greatly reduced. The World Wide Fund (WWF) recently reported that over-extraction by water companies is damaging Britain’s wetlands and trout rivers. The problem is most apparent in the South East where the population is increasing and the need for new housing is putting extra pressure on the decreasing water supply. Rainwater harvesting also reduces the need for the pumping of mains water which causes pollution and CO² emissions. Rainwater management can lower the volume of water in sewers and storm water run off is reduced helping to solve flooding.
Water rates look likely to continue their upward trend therefore rainwater conservation begins to look more attractive to the homeowner. Over half of all domestic water usage such as washing machines, toilets and gardens doesn’t require treated water from the mains supply. The case for harvesting rainwater speaks for itself: by conserving rainwater, the potential savings in water rates are very significant and, more importantly, the dependence on mains water is diminished. Sustained water savings can add value to a property as well as demonstrating a level of commitment to helping preserve the environment and its natural resources.