22 March 2017

The UK climate makes it easy to think of water as a plentiful resource that we don't need to worry about. This couldn't be further from the truth - according to Waterwise the UK has less available water per person than most other European countries. London is drier than Istanbul, and the South East of England has less water available per person than the Sudan and Syria.

The problem is, while the planet has an abundance of water only 3% of it is fresh (and just one third of 1% of this fresh water is suitable for human use, the rest trapped in glaciers or deep within the earth). In other words, if all the world's water is represented as 100 litres, just half a tablespoon is fresh and available for our use.

Just how much water do householders use?

In the UK the Environment Agency estimate that every person uses around 150 litres of the stuff a day and that's been rising by about 1% since the 1930s. If you take 'embedded water' (used to produce the food and products you use in your daily life) into account, it's estimated the figure is actually 3,400 litres.

So how does our daily consumption stack up? Toilet flushing and personal washing make up the lion's share (30% for toilets, 21% for baths/taps and 12% for showers respectively), clothes washing accounts for 13%, washing-up 8%, outdoor use 7% with drinking 4% and other uses accounting for the remaining 5%.

How can we use water more efficiently?

This week (20-24 March) marks Waterwise's third annual Water Saving Week raising awareness of what we can all do to conserve supply.

Behavioural changes can obviously make a big difference - a tap left running while teeth brushing can waste six litres a minute and taking a shower can use a third of the amount of water needed for a bath - but what difference can designers and specifiers make to help householders reduce the amount of water being wasted while not restricting use? In other words, how can we make optimal choices for water efficiency without the end user spotting any discernable difference in performance or needing to change behaviours?

What does the legislation stipulate?

Approved Document Part G stipulates requirements for washing facilities and hot water services. Conservation is focussed on cold water supply, water efficiency, hot water supply and systems, sanitary conveniences and washing facilities, bathrooms, kitchens and food preparation.

Water metering is now compulsory on new buildings and serves to make householders more inclined to try and conserve supply to reduce costs.

Approved Document G (Amendment 17k) stipulates that in new dwellings the maximum allowable consumption of potable water is 125 litres per person a day. With 150 litres the average consumption, legislation is, therefore, looking to decrease consumption in the order of at least 25 litres.

Local Authorities are also encouraged to consider water availability in their development plans.

How can we design and specify for water efficiency?


House builders generally choose shower fittings with the performance of power showers due to customer demand. Some manufacturers claim that their showers have the feel of power showers, while delivering a lower volume of water. This is achieved through a combination of air entrainment or other technical features to limit water use with little detriment to performance.

It should be possible to  easily specify a shower that uses < 10 litres / minute.  If relying on mains pressure (around 1.5 to 2 bar) then it is possible to specify shower heads that provide a 'power shower' type experience but limit the water used. Showers using pumped water are regulated by the specification of the pump - some are capable of generating 24 litres / minute (double that of a typical power shower) so are not the best choice for water conservation.

Water consumption obviously varies according to water pressure - the heating mechanism (in regard to warm-up time and length of pipe runs), the type of controls (seperate flow and temperature controls offering greater flexibility) and flow rate (influenced by mains or pumped pressure and the spray pattern achieved through the shower head) are all influential.


Householders typically take more showers than baths but when it comes to bathing, a typical bath requires a fill of around 80 litres. For those looking to conserve water, there are a number of 'water-efficient' designs that use shaping to reduce the volume of water required.

Indoor taps

Spray or water efficient taps are well worth considering, particularly in scenarios where hand washing is the primary use (for example, a downstairs bathroom) delivering a potential flow as low as 1.7 litres /  minute. Variable flow rate taps offer more flexibility in the bathroom or kitchen where the need is likely to be a quick fill of a basin.

Outdoor water use

Harvesting water by means of a water butt system should negate the need to rely on tap water for most outside uses. Clever use of horticulture (selecting drought-tolerant plants and use of mulch to conserve soil moisture) will also help reduce the need for watering. Where outside taps are supplied, flow limitation can help prevent wastage.

Toilet flushing accounts for a sizeable proportion of a householder's daily water consumption

Toilet use

Flushing appliances must meet the requirements of the Water Supply (Water Fittings) Regulations 1999 which stipulate a use of 6 litres per flush (and a secondary flush, on dual-use toilets, should provide no more than two thirds of the full flush). Use of a 4.5 single flush or 6/3 or 4/2 dual flush system should make a major contribution to water efficiency measures and deliver a maximum use of 18-20 litres per occupant per day, and exceed the regulation requirements.

Choice of white goods - washing machines and dishwashers

Manufacturers of dishwashers and washing machines have made big improvements in both energy and water efficiency without compromising overall performance.

Efficient washing machines use far less water than the Water Supply (Water Fittings) Regulations 1999 stipulate - many now use less than 8 litres per kilogram, a significant reductiuon when you consider a typical maximum volume of 48 l/kg.

Dishwashers using less than 2 litres per place setting are not hard to find and offer savings far in excess of the 4.5 litres per setting set out in the regulations.

Householders can play their part in conserving water by only powering full dishwasher loads

Rainwater and greywater

While a water butt may be an appropriate measure for a single residential dwelling, multi-occupancy or commercial properties offer the opportunity to make more of natural resources through rainwater harvesting from impermerable surfaces such as roofs and recycling of greywater from sinks, showers and baths that can be collected, treated and then reused. These options need to be properly considered at planning stage to determine whether a dual pipework system is required.