Collecting rain water

Collecting rainwater is a very old practice, people have always found ways of harvesting rain. Rainwater collecting systems existed in Palestine and Greece 4000 years’ ago. In ancient Rome, residences were built with individual cisterns and paved courtyards to capture rain water to augment water from city’s aqueducts. Ruins of cisterns built as early as 2000 BC are still standing in Israel. Wars have been been fought over ownership of water; it has been said that water may be the oil of the 21st Century.

Our water resources are dwindling for many reasons: the periods of drought are more frequent, our demand is increasing, the groundwater table is more pollutated.

The price of water has rocketed and has increased by 5% in the last 15 years. With an average consumption between 150l and 200l per person, the annual budget for a family of 4 is around £600.

How can you save water?

  • You must be on the look out for any leak. A leaking tap is approximately 100l of water lost in a day. Have a shower instead of a bath means you use only 50l of water instead of 150l.
  • You have to change your habits. When brushing your teeth, don’t leave the tap on and you will save up to 30l of water. Take a shower instead of a bath- a conventional shower (as opposed to a power shower) uses around two-thirds less water than a bath.
  • Only use the washing machine and the dishwasher with a full load. When buying new appliances, consider those that offer cycle and load size adjustments. They’re more water and energy efficient.
  • Fix anything you find leaking. A leaking toilet is 1000l of water wasted per day.
  • Wash your car with a bucket instead of a hose
  • You can buy water saving devices. A dual-flush toilet will use between 3l and 6l of water instead of 10l. An energy-efficient shower head with an aerator use 40% less water with the same comfort.
  • Use a watering can in the garden – hosepipes use up to 540 litres of water an hour ( a watering can only holds around 10 litres) and try to use ‘grey water’ when possible.
  • To avoid having to run the tap for a cool drink keep a container of water in the fridge.
  • Insulate your water pipes. You’ll get hot water faster plus avoid wasting water while it heats up.

Collecting rain water but what shall I use it for?

Rainwater can be used for many outdoor tasks such as watering gardens, washing cars and patio or filling your private pool. Inside your house you can use rainwater for the supply of toilet and washing floors, and on an experimental basis for laundry .
Unlike tap water, rainwater does not contain limestone or chlore. It also has the huge advantage of being free. The potential of rainwater is important since you can collect around 45 and 80 m3 for a 100 m² roof. It will ensure, in theory, all the watering needs of a 200 m² garden if the rains are well distributed, or if you have a tank with sufficient capacity.

Ways of collecting rain water


  • Water butts: A very simple way is to install a water butt linked by a diverter to a down pipe.You can buy a barrel shaped collector which will hold between 100 to 300l of water.
  • RWH systems, rainwater harvesting system, with a system of pipes collecting the water from the roof and taken to a storage tank. A filter is installed to remove leaves and other debris. You can pump water directly to your house; a float switch will automatically top up with the mains water when the level is too low. Either a large above-ground tank which can holds up to 2000 litres or an underground tank which can store several thousand litres of water and requires a pump.Although it falls from the sky, rain water does not escape pollution.Rainwater will pick up pollutants while running down your roof, mercury from coal burning buildings and power plants, dioxins, bird and other animal feces. Rain water does not meet the standards of quality of water intended for human consumption .
    For the sake of caution, the use of rainwater remains prohibited inside the establishments of health, social and medico-social, retirement homes, surgeries, dental offices, blood establishments, medical biology analysis laboratories, or nurseries and primary schools.

Rain water is not a drinking water!

What do the regulations say?

There are no UK regulations concerning rainwater use for toilets, washing machines and gardens, though the back-up from the mains must be in accord with standard regulations.
If you are far from mains water, or don’t fancy chlorine or fluorine in your drinking water, a UV unit costs around £500, and you have to change the bulb each year.


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