Understanding Shower Valves

Understanding What a Shower Valve Does

A shower valve is that part of the shower which controls the flow and mix of hot and cold water into the rest of your shower. It does this using a combination of diverters, flow controls and temperature controls.

How does it do it – Diverters, Flow Controls and Temperature Controls

Temperature Control

All valves usually have a single temperature control. The temperature control varies the proportion on hot and cold water that is mixed allowing the temperature of the resultant mix to be controlled. Once the water has been mixed by this part of the valve various flow controls and/or diverters then direct the mixed water to the various functions of the shower. (By function we mean any of the shower outlets, e.g. overhead shower, slider rail, body jets etc).

Flow Control

A flow control is simply a valve controlled by a handle or lever on the valve. It takes water that has already been mixed by the valve and restricts its flow from full off to full on allowing fine control of the rate of flow between these two extremes. Each flow control generally controls the rate of flow from a single valve outlet and from there to a single shower function. To control a shower with two functions such as an overhead shower and a hand-held shower one option is to use a shower with two flow controls, each flow control independently controls the rate of flow to a single outlet, this means that you can have both controls on at the same time, this is in contrast to diverters (see below).


A diverter is a switch used to direct water that has already been mixed in the valve to one of two or more valve outlets. A two-way diverter switches water between one of two outlets and a three-way diverter switches between one of three outlets. In addition a diverter has an off position which cuts the supply of water to all the showers outlets. Diverters do not supply water independently to the shower outlets, only one can be on at a time. In addition diverters do not allow fine control over the rate of flow, although there may be some control each outlet is basically full on or full off. Note that in many shower configurations especially those with an exposed valve (see below) there may be another separate diverter on another part of the shower, (usually on the riser which takes the water up the wall) which switches water from the valve between two shower outlets, for example an overhead shower and a hand-held one on a slide rail or wall mount.

Sequential Shower Valve Controls

Most showers have at least two controls, a temperature control and one or more flow control and/or diverters however a sequential shower valve has a single lever control combining temperature and flow control regulation, As soon as a sequential control is turned the flow to the shower is turned full on cold as the handle is turned to its full extent the flow remains on full flow but the temperature is increased to its maximum. With a sequential valve the temperature con be controlled finely but not the flow.

Thermostatic and Manual Shower Valves

Thermostatic shower valves include an inbuilt anti-scald safety mechanism which cuts off the flow of water if the temperature of the mixed water exceeds a (usually) pre-set value. Manual valves do not provide this safety feature. Some thermostatic valves also allow the water temperature to be set and maintained.

In general a shower will be supplied water from the same mains system and boiler as all the rest of the plumbing in the house, this means that changes in water usage in other parts of the house can effect the flow of water to the shower and more particularly can cause a reduction in the supply of cold water to the shower. This results in the mixed water being delivered by the shower containing a higher proportion of hot water meaning that the water temperature rises. It’s in just such situations that thermostatic valves protect the use of the shower from injury.

Exposed and Concealed Shower Valves

Generally showers can be classed as exposed or concealed. A concealed shower is one where most of the pipe work associated with the shower is fitted inside the wall and in particular the shower valves shower outlets are inside the wall. An exposed shower by contrast has a shower valve with outlets on the outside of the wall and the pipe work supplying the various shower functions are visible.

Combinations of Controls on Shower Valves

There are four most common combinations of controls and outlets on shower valves and you need to pick the right one for the combination of shower features you are having in your shower. Here are the four most common types of valves and how you would use them:

1. Two Controls and One Outlet: One control is for temperature, the other for rate of flow it supplies one shower head only. But especially on traditional style exposed showers you often find a diverter on the rigid riser part of the shower so that one of these valves can be used with two shower heads for example an overhead shower and a hand-held shower on a slide rail.

2. Two Controls and Two Outlets: One control is for temperature, the other is a diverter which switches between the two different shower outlets. However the diverter does not give you as fine control of the rate of flow as a flow control. You would use this for two shower outlets for example an overhead and slider rail. But you might prefer to use the next options instead.

3. Three Controls and Two Outlets One control is for temperature, the other two are both flow controls independently controlling the rate of flow to the two different shower outlets. You would use this for two shower outlets for example an overhead and slider rail. It gives you finer control of the rate of flow than the 2-control valve with the diverter and you can have both showers on at the same time which you can’t with the diverter version because that one switches between them.

4. Three Controls and Three Outlets One control is for temperature, one is a rate of flow control and one is a diverter. Typically you might use this for a set up where you have an overhead shower with another hand-held shower that goes on a slider rail and a number of body jets (body jets are usually all supplied by a single outlet from the valve).

You might then have the flow control feeding the overhead shower and the diverter switching between the body jets and the hand-held. That means you could have each of them on separately or you could have the overhead shower on with hand-held shower or the overhead shower on with the body jets but not the body jets on with the hand-held. But how you have this plumbed-in is your choice, you just need to make it clear to your plumber.

There are other combinations too including sequential valves and valves with integrated outlets such as those which include a bath spout or a hand-held shower and hose. If you want anything unusual its always best to check that the components you get are the right combination to achieve what you want and for this you need someone who’s got the time to talk to you and who knows the subject area.