Marcus Zipperlen* offers some practical advice on how to use water more effectively in the home.

In Britain each of us uses around 150 litres of water per day in our homes.  Every year we use more and more because of our increasingly affluent lifestyles and tendency to live in smaller housing units.  There are environmental costs to this rising consumption and difficulties in maintaining water supply in drier parts of the country.  The simplest way to get around all these problems is for us all to use a bit less.  Fortunately, it is not difficult to cut domestic water use without compromising quality of life.  An easily achievable target would be 90 litres per person per day.

First things first: reducing demand   

For new build, water savings can be made through appropriate plumbing.  For example, insulating all pipes, both hot and cold, and placing hot water pipes above cold water pipes to minimise heating.  Flow regulation valves installed before taps and appliances can minimise wastage and balance water flows around the building.  If you have a pressurised system then use small bore (ten millimetre) pipe to reduce waste, making sure that you check the flow rate to any electric shower to ensure an adequate supply.  
  
Water-efficient toilets are key to a water-efficient house.  Although it is possible to have water-free, composting toilets, these are rarely suitable for the average home.

There are two main types of flush mechanism, siphon and valve.  Each has particular merits, depending on the situation.  Valve-operated cisterns allow for slightly greater water-saving than siphon, but they can and do leak if not maintained.  Hampshire Water report that six percent of leakage in its region is due to faulty valve toilets.   As toilets are a fit-and-forget item, low-flush siphon toilets that will not leak are a better option. 

Snazzy low-flush loos can be expensive (around £250) but there are low-cost ways to modify an old siphon toilet.  Cheapest is to put a displacement device in the cistern to reduce the flush volume. A filled drinks bottle with the lid on works well.  For £10-£20 you could install a variable flush mechanism to allow you a half flush, or install a delayed-fill inlet valve, which stops the cistern refilling before a flush cycle has completed and saves between one to three litres per flush.
  
For hand washing, spray or aerator taps work much better than standard taps and can reduce water use by up to 80 percent.  Aerator heads are cheap and fitted easily to modern taps with threaded outlets.  Tapmagic makes an excellent and inexpensive retro-fit, suitable for older taps too.  This gives a spray at low flows (for hand washing) but a full flow when the tap is open fully so can be used on the kitchen sink.

A Rolls-Royce solution is the water brake tap.  These have a lever which is easy to push to a certain point, and in this range the flow is low.  To obtain a full flow you must push the lever further, past a noticeable resistance point.

Showers generally use less water than baths, but not always.  A typical bath might use around 70 litres and a standard electric shower as little as 25 litres.
But a power shower can use upwards of 60 litres per use.  To reduce flows through the shower either install a water saving shower head or fit a simple flow restrictor.  Aerator heads imitate a power shower but some types retain fairly high flows (eight to ten litres per minute).  A simple flow regulator is the cheapest (around £2.50) way of saving water on a thermostatic mixer shower.
You should, however, never restrict the flow to a power shower without first consulting the manufacturer.

Re-use and recycling       

Untreated rainwater can be used for watering the garden, flushing toilets and in washing machines, potentially cutting domestic water use by 50 percent.  In practice most domestic roofs are too small to harvest this quantity of water.  Although it is technically possible to meet all your household needs from rainwater with suitable filtering and disinfection, it is rarely an environmentally- friendly option in the UK given the lifecycle costs of infrastructure and pumping.  It is often best to keep it simple and do no more than install water butts for garden use.  

Rainwater harvesting for non-potable use.   Water passes through a filter (a) and into the storage tank (b), from where it is pumped (c) directly to appliances (d).  A mains-water back-up (e) ensures continuity of supply

In a household there is a good match between the quantities of 'light' grey water (from showers, baths and hand basins) produced and that needed to flush toilets, offering the potential to save 30 percent of total water consumption.   But this virtuous recycling circle is hard to achieve in practice.

There are broadly two approaches to grey water treatment:

*Proprietary off-the-shelf systems to clean and re-circulate wastewater inside the house. All independent studies show that current technology is unreliable and cannot be justified on economic or environmental grounds.  If there is a future for domestic grey water re-use in the house it is probably going to involve district scale systems.

*Treating grey water similarly to sewage. One can use biological filters outside the property to clean water for garden irrigation.  Similarly, we have had success with direct, subsurface garden irrigation, although some careful design is needed.

The best advice when it comes to making your house more water efficient is to concentrate efforts first on cutting demand before seeking alternative sources.  Low-flush toilets and low-flow taps and showers are the basics.  When seeking to supplement mains water start with rainwater, and keep it simple, using a water butt or two.  Bringing rainwater back into the building may be viable with a large roof area, good rainfall and significant demand for non-potable water.  Grey water recycling is probably a non-starter and on a domestic scale the only sustainable option at present is to re-use it in the garden for irrigation.  Not only is water efficiency good for the environment but appropriately chosen solutions will save you money. So, you have nothing to lose.

*Marcus Zipperlen trained as a water and sanitation engineer and is Head of Biology at the Centre for Alternative Technology, Europe's leading Eco-centre.

For more information about any of the  water efficiency products and techniques mentioned phone CAT's free information service +44 (0)1654 705989.