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Our water saving article at Hubpages - read the Water saving SUDS (sustainable Urban Drainage Systems) pdf here >

Note this is using the previous name for this site 'Eco tist'


Rainwater can be harnessed for many of the same functions which greywater can provide with stored water being suitable for plant watering, toilet flushing and car washing.

Rainwater will contain significantly less chemicals and pollutants and as such will not require the amount of filtration that greywater requires. Rainwater is also completely infrastructure and cost free allowing every litre gained to make a saving to the building's impact on the environment.

Rainwater can be collected from gutters and channelled into storage tanks. This water is ideal for irrigation, being the same water that plant life would get anyway.

Plumbing a rainwater based system to provide flushing toilet water as well as washing machine uses is also not a difficult task and can be achieved from as little as £1000 for a DIY kit. A fully Integrated rain water collection system can reduce the amount of fresh water a building requires by 30-50%.

The amount of water available to a rainwater system can be calculated by looking at the amount of rainfall in an area and the surface area of the collection system/room. Total capacity can then be worked out using the formula '1 millimetre of rain on a 1 square meter surface yields 1 litre of water'. A home with 100 square meters of roof could catch as much as 130 cubic meters of rainwater.

This is an optimal figure however as rain water (despite seeming to be in England) is not constant and unless large storage tanks are used not all will be harvested. Every millilitre collected is free and prevents purified water from being used unnecessarily. Collection can further be increased by adding extra catchment systems around a building, for example a stand-alone collector in the garden.

It should be noted that collecting rainwater from rooftops in a SUDS approach prevents it from reaching the ground. In some areas such as cities this is beneficial as it reduces the load on drainage and sewage systems, however in other areas it may have a negative impact leading to soil erosion. This is uncommon but it should not be overlooked when fitting a rainwater collection system to a green build as low impact on the environment is highly sought after.

Rainwater collection systems will occasionally require some maintenance. This mainly involves the checking of gutters and drainage channels for sludge and vegetation (such as leaves) and the subsequent clearing.

It is also a good practice to occasionally flush the tank and give it a clean to prevent the possible build up of bacteria and mould (especially in garden based systems).

Inside a building

Household facilities which use water are often wasteful and when used in a green build consideration should be given to improving this inefficiency.

The most common of these is the toilet which uses nearly 30% of the total water that flows into a home. A typical UK toilet uses between 4 and 8 litres of water every flush. This is equivalent to the amount of water required to keep 2-4 people going for one day! Dual flush systems allow the occupants of a building to select the amount of water required for each given flushing.

These systems alone can result in a annual water saving of up to 30%, which could be 10,000 litres of water per person per year. Dual flush systems can be retrofitted onto existing cisterns saving on the need to replace it. More water efficient toilets using smaller cisterns and water distribution methods from around the rim are being introduced into the market and should be considered on a new installation.

Existing toilet cisterns can be upgraded using simple devices to displace some of the water in the cistern tricking it into thinking it has more water then it has. These can reduce water use by around 1 litre per flush which can work out to the equivalent of 35,000 cups of tea a year when fitted to an average family toilet.

These devices come under many colourful names such as the "Cistern Hippo" and "Freddie Frog" and are often available free from local water supply companies. A way to introduce children to water efficiency is to help them build a similar device using stones and an empty plastic bottle to displace the water.

Shower heads and tap fittings can be designed to use less water by building in an air venturi similar to a spa bath. This mixes air and water together causing the water to form air bubbles which are then coated in water. When these bubbles hit a surface they pop and the water sticks to the surface.

These systems feel the same as normal showers but use two thirds of the water a conventional show head/tap would use. This has a knock effect for green building as it means two thirds less water is required to be heated and pumped around the system in the first place.

Appliances such as washing machines and dishwashers will all require water in order to function. Newer models are significantly more water efficient than older models. Manufacturers will normally supply water usage figures to allow the most efficient device to be chosen.

Tumble dryers can be fitted with condensers to recover the water dried out of clothing, which can then be used in a greywater system, or for garden irrigation.

Paving and parking

A huge area of garden has been paved over in recent years to provide car parking. This is often to accommodate large SUVs or people carriers, or multiple cars, which are difficult to park in the street. This has caused an increase in flooding as rainwater is not absorbed into the ground at all, but flows into the old-style sewer system.

It is estimated that an area of over 22 Hyde Parks have been paved over in London in the last 10 years. New planning laws are coming in to prevent non-porous paving, which will require a planning application. Porous paving will not, and this will encourage people to use it.


In existing builds dripping taps and leaky pipes can account for a substantial water loss. With water metering on the way it is of utmost importance that leaks be found and fixed as soon as possible. Often a single 50 pence washer in a tap can result in as much as 9 litres a week being wasted.

Pipework should also be checked to ensure it is not leaking. An easy method to check for leaks in a metered property is to shut off the mains water, then take a meter reading and leave for a few hours. After some time has passed the meter should be checked again and if this shows water usage then there are leaks around the property.


Changing the attitudes of a building's occupants can also reduce water use.

Leaving taps running while brushing teeth or shaving pours around nine litres of water straight into the drain. Having showers instead of baths drastically cuts the amount of water used.

Fitting a shower timer will allow occupants to keep an eye on water usage even more.

Using a bucket and sponge to wash a car instead of a hosepipe will save gallons.

Only using washing machines when a full load is required will further cut back on fresh water used.

Using the minimum amount of pipework required to transport hot water around a building will reduce water usage by reducing the amount of cold water which is run off before hot water comes through the tap.

Currently in the UK water is quite low priced and conservation methods will often take a while to pay back the cost of investment at present rates. This is very likely to change in the future with more and more companies introducing water metering, water droughts caused by climate change and a growing population base competing for the same water resources will inevitably drive up the price.

Changing the way we view water combined with water saving technologies such as greywater and rainwater harvesting can only have a positive impact on the environment around us protecting it for generations to come.

See our other articles on water use when building, water conservation tips, and the pointless waste of bottled water.