Install a Mixer Shower

There are many types of shower that can be installed in a property. The following information is designed to aid in the process of selecting a shower by outlining the basic installation process required to install a mixer shower - it is not intended to provide detailed fitting instructions.*

Mixer showers take a hot water feed and a cold water feed from your heating system and mix them in a chamber within the body of the shower. Levers or dials are then used to control the rate of flow and the temperature of the mixed water.

It is important to buy a shower mixer valve that is suitable for use with the heating system you have in your property. Most central heating systems also heat your hot water but not always - for example you might have electric radiators and an immersion heater to provide hot water. The most common hot water systems are:

standard vented cylinder - low pressure stored hot water, low pressure stored cold water

combination boiler - no stored hot water, no stored cold water

unvented cylinder - mains/high pressure stored hot water, mains/high pressure cold water

All shower valves will have upper and lower pressure limits depending on which type of system they are designed to operate with. Some are designed for low pressure only, some for high pressure only, some for combination boilers only. Some mixer showers will be suitable to install with one, two or all three of the different types of hot water systems so be sure to check before buying. Most will require that the pressures of the hot and cold feeds to the valve are nominally equal to ensure that the water mixes correctly (if you have unequal pressure a venturi shower might be more suitable). If you have a low pressure hot water system it is usually possible to boost the pressure by installing a shower pump for use with an appropriate mixer or you could fit a composite power shower which is basically a mixer valve and pump in one box.

There are many different designs of mixer shower but they tend to fall into two categories: recessed and surface mounted. Recessed shower valves are designed to be used on hollow walls which enables the body of the valve and the supply pipes to be housed behind the wall giving a neater overall appearance. They are ideal for use in a small shower cubicle as there is less protrusion into the enclosure which can be important when space is limited. With surface mounted shower valves the body of the valve is visible. The pipework can be fitted on the surface but these valves usually allow the supply pipes to be fitted from the rear as well (so that the valve is exposed but the pipework hidden). If the pipework is to be run on the surface there is chrome plated copper pipe available to help make the job look as good as possible. There are some mixer shower that are supplied with a cover plate enabling them to be used in a surface mounted or recessed situation.

The temperature of the water delivered by the mixer valve can be affected by changes in pressure caused by other appliances in the home calling off water from the same supply. One solution is to supply the shower with dedicated feeds from the cylinder and cold tank. Thermostatic shower mixers can also help overcome these temperature fluctuations by keeping the temperature almost constant and in some instances it will stop the flow in the case of a failure of the cold supply (to prevent scalding). Mixer valves that are not thermostatic are referred to as manual.

Bath shower mixers essentially act like a manual mixer valve with a diverter to switch between bath and shower. If you have stored, low pressure water and the cold water tank does not provide enough head some diverters that are held in position by the water pressure will have difficulty remaining in position.

See the following pages for more information on installing each of these showers:

*There are many rules and regulations that govern the installation of bathroom, plumbing and electrical components. These vary from time to time and also from country to country. Always use a qualified tradesman to install plumbing or electrical components to ensure your products are installed in accordance with the local regulations applicable at the time of installation.