How Does a Shower Valve Work?

How does a Shower Valve Work

If you’re not familiar with plumbing, you may think that a shower is easy to operate. You use water, shampoo your hair, soap down, and rinse off. Letting the water and soap suds go down the drain. It’s simple, some parts can quit working or clog the drain. To know more about how a shower operates, you should learn how does a shower valve work.

Where is the Shower Valve?

Whether the shower is a stand-alone type or is part of the bathtub, there are shower valves, including the diverter valve, which helps control the temperature and flow of the water. There may be a single valve to control the water flow. And temperature or some showers have two or more valves to manage how the shower works.

For showers with more valves, there may be knobs usually marked with “H” for hot and “C” for cold. The third valve is called a diverter valve which controls the water flows that comes out of the bathtub spout or from the shower head.

How Does A Shower Valve Work?

In stand-alone showers, there is usually only one valve that controls the water flow and temperature. It works by turning or pulling out the handle to start the shower. Turning the knobs to control hot or cold water that runs from the spout.

Most new showers have devices to control the temperature of the water to prevent getting scalded by hot water. If there are young children or older adults in the household, their skin is very thin. They can easily scald if the water temperature is too high.

Types of Valves

Most new shower models have a shower valve that limits the water temperature and controls the water flow. These valves may be pressure-balance or thermostatic valves.

Pressure-Balance ValvesPressure-Balance Valve

It controls the water flow by controlling the ratio of hot and cold. Pressure-Balance valves ensure no one is scalded by the water, there is a set-screw. Allowing a sleeve to open and close as the person in the shower adjusts the temperature of it. If the handle of this valve is turned fully to the hot side, cold water stops entering. And set point for hot to prevent from getting hotter. The valve operates the opposite way if someone is taking a cold.

Water pressure reduces by turning on the cold tap over the kitchen sink or flushing the toilet. It affects the temperature of the water in the shower. The lack of cold triggers the pressure-balance valve, and reduces the amount of hot flowing through the system.

Thermostatic ValvesThermostatic Valve

The shower user is able to manage the water temperature better with this type of valve as the pressure-balance valve doesn’t have anything to do with controlling the temperature.

Thermostatic systems have two valves, one that controls the flow of water and the other that controls its temperature. This system reacts to the temperature of the water and not the water pressure, as does a pressure-balance valve. There are four components within a thermostatic valve that controls the water’s temperature:

  • Thermostatic Element
  • Piston
  • Return Spring
  • Temperature Control

Thermostatic Element

Thermostatic element is usually made from wax, which reacts to the higher water temperature by expanding. As it expands, it reduces the amount of hot water mixing with cold. This component is attached to a piston.


As the thermostatic element expands, it is the piston’s job to cut off the amount of hot water mixing in with the cold to control the water’s temperature. Consistently, it mixes well.

Return Spring

A return spring works the opposite way of the piston. To increase the amount of hot water and to ensure a consistent temperature.

Temperature Control

The user controls the position of the piston by turning the dial to increase or decrease the amount of hot water mixing.

Diverter Valves

The diverter shower valve has nothing to do with the water temperature. It only controls where the water is flowing from in a shower/bathtub combination. The diverter valve usually pulls up, or that can be turned to shut off the water flow to the tub and divert it to the showerhead.

Diverter ValveIf you are retrofitting a tub with a shower, you will need to install a diverter valve to use the shower. You’ll need to choose from one of three different types of diverter valves:

  • 3-Valve Diverters
  • Two-Valve Diverters
  • Tee Diverters

3-Valve Diverters

A 3-valve diverter is installed between the hot and cold taps of a shower/tub combination. 3-Valve Diverters allows the water to be diverted to the showerhead, the tub spout. Or allow the water to flow through the spout. This type of diverter has a handle that turns to change the water flow.

Two-Valve Diverters

The two-valve diverter works the same way. As a three valve to divert water from the bathtub to the showerhead. The L-shaped diverters push the water up to the shower arm.

The diverter can either set between the taps if there are two that control the water temperature. The face plate on the dial indicates which way to turn the dial by using red for hot and blue for cold.

Tee Diverters

A tee diverter is a single-valve that within the spout. The user runs the water into the tub to mix well. And pull up a knob to divert the water from the tub, it flows up the pipe and out the showerhead.

Repairing a Diverter Valve

After a few years of operation, the diverter valve on a bathtub can leak water into the tub as you’re taking a shower, or it may not divert the water to the showerhead at all. Fixing this problem is simple, you don’t need to pay a plumber $50 an hour.

In-Spout Diverter Repair

The easiest way to repair the valve is to replace it. Usually a screw on the bottom of it that holds in place. Use an Allen wrench to remove the screw.

For spouts that don’t have a set-screw, you need to use a pipe wrench to remove it. Turn the wrench counterclockwise; you’ll be able to remove the spout from the water pipe.

Take the spout with you to buy a replacement to ensure the diverter is located in the same place. Replace the spout, by either turning the wrench clockwise to install it.

A problem with a pressure-balance or thermostatic shower valves may be difficult to detect. Other issues can cause a lack of hot water, debris coming from pipes, or water temperatures reversed that comes from hot and cold taps.

In these cases, you may need to hire a plumber to fix it.


  1. i have a 4 way dirverter valve in my shower and went to turn it on this morning and heard a thump and no water is coming from the hot side, so guessing something broke inside the valve, is there a kit for replacing the internal parts of the valve or do I replace the entire valve?

    1. I’m sure there has to be a repair kit for your valve. What’s the brand and model number? You may have scale build-up in the valve. Try shutting off the water and cleaning out the valve. That may do the trick.

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