Environmental Information Exchange

Reducing water use for building users

These pages contain information on reducing water use for taps, toilets, urinals, and showers and baths.

Efficient taps

Taps use water at varying rates depending on the flow. Taps can also be left on by users or even leak. However, there are a number of types of taps that are more water efficient.

Sensor taps
These taps use a motion sensor to detect movement and provide water. When there is no movement, the tap is off. This type of tap is generally used for washing hands in toilet areas. Sensors can be set with different sensitivity as well as flow rates and temperature of water. The most efficient sensors taps have set all of these so that users are able to wash hands efficiently.

Push taps / Push button taps
These taps use a mechanism that, when pushed begins the flow of water from the tap then automatically shuts off after a short period. Most push taps are mechanical and do not require energy to run. However, some models can require more maintenance than most water saving taps.

Dripping taps

A dripping tap can waste as much as a litre per hour (European Environment Agency) or 8760 litres per year!

Taps generally drip for one of two reasons: a damaged washer or a damaged valve seat. Fixing dripping taps is usually quite simple and can often be done without recourse to a professional plumber. A very useful illustrated guide can be found at www.juliancassell.com.

Although dripping taps are easy to fix, many organisations are so large that checking for dripping taps is not a routine task. Wasted water from dripping taps can be reduced by making regular maintenance checks as well as encouraging users (staff or public) to contact maintenance to report a dripping tap. By making this an easy contact and notifying staff (and the public) that they are encouraged to report this, wasted water, as well as the energy used to heat water will be reduced.


Efficient Toilets

In order to understand where water savings can be made with toilets, a number of steps need to be taken.  To determine how much water existing toilets use both the toilet cistern and flushing mechanism need to be reviewed.  Often efficiencies can be made without replacing the entire toilet.

Flush volume
For older toilets the volume of a toilet uses may not be clear by just inspecting the toilet cistern. Further, it is not always clear whether reducing the volume of water used will detract from proper functions of the toilet. To estimate the size of the toilet cistern (if this is not labelled inside the cistern) use a ruler to take measurements (in cms) depth, length, and width of the inside of the cistern. Multiply these together and divide by 1000 to get an estimate of the number of litres.

Flush volume can be offset with ‘hippos’ and other displacement devices placed in the cistern. A device in the cistern displaces an amount of water reducing the need to refill the tank after a flush. A hippo (or heavy object such as bottle of water) can offset 1 - 2.5 litres per flush. However there is some debate around the use of offsetting water saving devices.

These devices can only be used in 'standard' toilets, not low flow toilets, so before considering using such devices it is important to know the volume of the toilet. If displacement devices are used in low flow toilets the function of the toilet will be reduced, meaning that multiple flushes will be required to clear the pan - meaning the toilet will actually use more water with the device than without it.

Plastic hippo devices can also degrade over time so need to be replaced periodically. The British Bathroom Manufacturers Association only recommend the use of displacement devices as short term solutions to reducing water use in toilets, and long term water efficient can be achieved using more permanent solutions.

Flushing mechanism
There are two main methods of flush: a valve or siphon.

Valve flush
In 2001 it became legal to sell and fit 'valve' toilets in the UK in addition to traditional siphon toilets. However these valve toilets can leak when the rubber 'flapper' valve perishes. The frequency for replacement of this valve varies depending on the toilet and the water area. Replacement involves additional costs of maintenance and the inconvenience of out-of-use facilities.

However valve toilets have the benefit of 'dual' flush. This allows users to select the amount of flush required to clear the pan. In practice, in the UK many users are not aware of how the system works and may end up flushing multiple times to get the same effect - removing any water saving benefits.

Siphon flush
Siphon toilets have the benefit of being extremely durable and very unlikely to leak. They can be converted to dual flush or interruptible flush, but as standard the level of water used is determined by the size of the cistern (which has a predetermined volume of water sufficient to clear the pan). When replacing toilets chose those tested to work at lower volumes. There are a number of steps that can be taken to improve the water efficiency of siphon toilets:
Retrofit a water saving device such as the Interflush, Mecon Water Saver and Thomas Dudley Turbo88 to allow a toilet to be flushed only as much as required. The user flushes the toilet as normal and release the flush when the bowl is clear. These devices cannot be fitted to valve toilets. For any retrofit device it is important that users understand how the system works, so installation of new systems should be accompanied by adequate signs and information to staff to allow water savings to be made.

Leaking toilets

There is a very simple way to detect leaks in the flapper valve of a valve toilet without recourse to a plumber:

1. Remove the cistern lid, then flush the toilet
2. After the flapper/tank ball drops and the tank refills, add several drops of dark food colouring
3. Wait 20 minutes
4. If a trace of the colouring appears in the toilet bowl, there is a leak in the 'flapper' valve.

Traditional siphon toilets require very little maintenance and do not leak. If there is a problem with a valve toilet it will not flush at all, rather than leaking.

Efficient Urinals

Urinals use water to flush using varying amounts and frequencies. Water use can be reduced by more effective controls for urinals.   Waterless urinals This type of urinal uses little or no water for flushing. By design, odours are trapped to reduce smell.   More information on waterless urinals can be found at the Green Building Store Website, the Construction Resources Website and the Waterless Urinals Website.

Urinal controls
Traditional urinals flush regardless of use. Many organisations will be unaware of this control and therefore not take steps to upgrade.

Urinals flush using an automatic syphonic cistern. The cistern is filled by a continuous flow of water, determined by the size of pipe running to the cistern, or in some cases, how open the tap on the pipe is set. Once the level of water reaches a fixed level in the cistern, syphonic action begins and the water in the cistern is flushed to the urinals. The cycle runs continuously 24 hours a day regardless of whether the premises are occupied.

However, it is possible to install more sophisticated controls to flush urinals. These can either be set on timers, or can be movement activated both systems trigger urinals to flush only when necessary.   A number of suppliers of urinal controls can be found on the internet.
Efficient showers and baths


Showers can be made more water efficient by restricting the flow of water or the duration of the shower. One shower type that restricts the flow of water as an aerated showerhead. Air is added to the flow of water to provide the same feeling of flow while using less water.
Similarly a low flow showerhead increases the force of the flow of water but reduces the quantity. This also results in providing the same feeling of flow while using less water. Aerated and reduced flow showerheads are available from a number of manufacturers. Note most models are not suitable for use with electric or low pressure showers. 


It is much more difficult to save water with baths because enough water is needed to immerse the user. One method of saving water in baths is to use more efficient bath design such as a low water volume bath. These are designed to provide a comfortable bath while using less water.   A number of companies offer low water volume baths.