Bathrooms Showers: Water Supply

A shower has to have two sources of supply – hot and cold water. These are mixed either manually or thermostatically to provide a spray at comfortable temperature.

One method of intermingling the flow is with a mixing set. This allows the flow of hot and cold water through two valves or screw-down taps. It is advisable to set the water flow to the pressure and temperature required before entering the cubicle.

Open the cold supply and then turn on the hot service until the required temperature and spray force is reached. A fluctuation of pressure on the supply could affect the mixture setting and produce dangerously hot water.

Thermostatic mixing valves, though far safer, are much more expensive. While not dependent on separate supplies, they are best given ‘first-pull’ call on the system. Temperature settings are maintained regardless of fluctuations of pressure. Most mixing valves have a separate control which allows the spray force to be varied.

To provide the correct pressure, there should be a minimum ‘head’ of water of 900mm, though l.22m to l.52m provides a more forceful spray.

The ‘head’ is the point from the base of the cistern to the top or head of the spray, to provide pressure for the most common type of spray, the rose. An ‘atomized’ spray, which is much finer, needs a minimum head of 2-45m. If the distances are reduced, the water may flow inefficiently.

Most shower units require supplies using pipes of 15mm bore (10mm in plastic), though some may need 22mm supply to maintain an adequate water force. If bends in pipework are likely to hamper supply, the larger size will be needed.

Mixing valves operate in a similar fashion to mixing sets and thermostatic mixing valves-except that the water-mixing and temperature settings are controlled through a single regulator.

The dangers from fluctuating pressure also apply to mixing valves and sets. Only a thermostatic valve can overcome this problem.

Showers should be connected to the low-pressure side of the domestic system -the storage cistern-and the pressure of both hot and cold water should be as even as possible.

Connection to the mains is forbidden in the UK but this is not the case in certain other countries. Where mains connection is made, there is no corresponding problem of maintaining pressure, since the rising main is usually of a high pressure.

In the atomized units, the water droplets are atomized by centrifugal force. The rose-type head breaks up the main body of water and distributes it in a maze of tiny droplets. It is pleasant and invigorating and is achieved by forcing the flow of water through many small holes in the headplate.


To connect up a shower arrangement to the existing plumbing system, you must empty existing pipes. Turn off any cistern stopcock, or tie up the ball valve and drain the cistern down. Open all the hot-water taps; this will drain off the water in the crown of the cistern, which will be sufficient.

Usually, the system can be connected most easily by means of tee-piece connectors. If there is a heavy storage-water demand or the pipework follows a long and tortuous route, it may be advisable to fit a separate supply pipe from the cistern. This will require complete emptying of the cistern, and a new connection will have to be made about 50mm up from the bottom.

It is possible to chase out wall surfaces and sink in pipes, or they can be boxed in behind the shower walling. It is essential that these should be accessible for maintenance and this is best done by fitting removable panels or tiled sections on to panelling which can be removed. Tiled panels can be drilled and fixings made by cupped chrome-headed screws.

Where pipework has to show, it can be painted to disguise it or stainless-steel tubing may be left exposed; this can look quite attractive.

Testing all installations before final concealment or boxing in of pipes is important. Where possible, it is much better to conceal all pipework, and many shower fitments provide for hidden supplies, taken in at the back.

Where you contemplate installing a shower in an upstairs room, it may be difficult to provide the desired water head. This may be achieved by raising the height of the storage cistern by placing it on a stout platform. This, of course, means draining down the system, extending and, possibly, re-routing loft pipework.

If the pipe run to the shower is long and there are a number of bends, it may also be advisable to increase the height from the minimum to compensate for possible pressure loss.

Waste outlets should be taken into a waste trap which has a minimum diameter of 38mm. There must be access to the trap for cleaning and a tubular trap is preferable to a bottle trap, since the latter may block up more readily on shower installations.

A slight drainage fall (1:80) must be maintained to connect up with the plumbing services, which, in modern practice, should be to the main soil system. In older systems, the water may discharge into a hopper head.

Wastes can be plumbed in copper or plastic but the latter is quicker, cheaper and simpler.

The fitting of the waste outlet follows the same technique to that of a bath or sink waste.

Lighting in showers must be of the enclosed pattern. Any internal lighting should be controlled by a pull switch. If using a light switch it should be located safely outside the bathroom.

Wires and light bulbs should not be exposed: light bulbs can explode if subjected to splashing.

10. November 2011 by admin
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