DoE PROJECT 10B WATER ECONOMY Interim Report 11727/1
Report No DWI0709/1



There are many different types and designs of WC being installed around the world. These include models made of different materials, including for example stainless steel, and models with various flushing systems, some using little or no water.

The most important types are however water flushed vitreous china models. The most common flushing arrangement is for flushing water to be supplied from a cistern or tank, normally using the force of gravity. WCs are produced in different arrangements depending on consumer preferences / traditions in particular countries. The main types of arrangement are:

There are two main approaches to WC pan design:

The volume of water used for flushing has reduced in many countries over the past 10 years or so with greater attention being paid to water conservation. A 6 litre flush volume is becoming the norm in many European countries and is the maximum allowed for most installations in the U.S.A. and most of Australia and New Zealand.

The outlet from a cistern or tank, providing flushing water by gravity, is normally through a valve - a simple flap (or flapper) type in the U.S.A. and areas of American influence or a more complex drop valve in Europe and Australasia. The valveless syphon required in the UK is found in few other countries.

Pressurised flushing valves, often connected to the mains, are used in many countries, particularly for public toilets.

In North America a popular design uses mains water pressure to compress air which is then used to provide a "pressure assisted" flush.

Interruptible flush, which can provide a shorter flush where there are no solids, is common in a number of European countries. Dual flush is also available in some European countries and a two button dual flush mechanism has become the norm in Australia and New Zealand.

The performance of various designs which achieve a 6 litre flush volume will clearly be of interest. It will also be necessary to assess the reliability and tendency to water leakage of the flushing mechanisms used with these designs.

Product now being installed in Australia and New Zealand may be of particular interest because WC pan designs have been developed from those of British manufacturers.

Copies of this report may be available as an Acrobat pdf download under the 'Find Completed Research' heading on the DWI website.