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Thermostatic Shower Buying Guide

By UJJBARAN October 23, 2021

Showers have fast become the focal feature of our bathrooms thanks to their ease of use and, in many cases, mobility benefits.

There are various types of shower, however, and one of the lesser-known designs is the thermostatic shower. A thermostatic shower is a type of mixer shower, that is fed via a property’s hot and cold water supply with an internal valve to mix them.

But just what is a thermostatic shower and how does one work? There are many questions around this shower type, so, We have made a complete guide to help you understand how a thermostatic shower functions and what you need to know prior to buying one.

Read on to learn more about thermostatic showers, how it differs from other types, how to fit one and much more…

What is a thermostatic shower?

A thermostatic shower is a type of mixer shower which features a thermostatic valve that maintains a constant water temperature.

The thermostatic valve is what makes this type of unique, mixing both hot and cold water together to a consistent and predetermined temperature. By doing so, this prevents scalding and cold shock which makes it extremely well-suited to families with young children or the elderly. This is, therefore, a safe multi-generational shower.

In short, if your shower is prone to running either too hot or cold or even consistently fluctuates in temperature and suffers from unusually low water pressure, a thermostatic shower could be the answer.

How is a thermostatic shower different from a mixer shower?

A manual mixer shower will mix hot and cold water to a set temperature but, unlike a thermostatic shower, it cannot react to sudden changes in temperature. A thermostatic shower instantly reacts to a change in water temperature and adjusts the water accordingly to get it back to the pre-set temperature. This avoids the threat of scalding or cold shock.

Thermostatic showers are more reliable for controlling temperature and avoiding potential injury.

What’s the difference between a thermostatic shower and an electric shower?

Thermostatic showers differ from an electric shower in a number of ways, the main difference being that they rely on a mains water supply to operate. A combination of water pressure and temperature allows a thermostatic shower to function.

Unlike a thermostatic shower, electric showers have their own heating element - which is usually seen in a box on the wall - so they only need a cold water supply, whereas thermostatic showers need hot and cold water.

Electric showers, however, can be more economical as the temperature is not affected by water usage in other parts of the house.

How does a thermostatic shower work?

Thermostatic showers store water at a high temperature before mixing it with cold water in a valve to a temperature that you have pre-set. 

Along with mixing the water together, the valve will also instantly react to changes in water temperature. It will immediately adjust the mixed water to return it to the pre-set temperature. It is this feature that makes a thermostatic shower the most reliable and controller-friendly.

Thermostatic shower valves will also shut down immediately should the cold-water supply fail. This is done in order to avoid injury to the user, such as scalding, by the hot water. This built-in safety system marks thermostatic showers out among other types as family-friendly and multi-generational.

Each thermostatic shower has core elements, which are:

  • Element: sensitive to the temperature of the water flowing through it, the element increases or decreases in size.
  • Piston: working in tandem with a spring, the piston moves across the hot and cold water entry points to regulate the water temperature as the element increases or decreases. The piston is key to maintaining a constant temperature.
  • Temperature control: this is the part of the valve that you can see and control - like with all showers. The control moves the piston, changing the hot and cold water mix.

These elements work together to keep the temperature you have selected at a constant and adjust where necessary.

ALFI brand 3 Way Thermostatic Shower Set with Body Sprays AB2287


What are the types of thermostatic shower valve?


Bar Valve

Bar shower valves feature slimline controls and a compact size that make them an excellent choice for small bathrooms. Easy to fit, these valves are often the cheapest of the thermostatic valves and come in a variety of materials, including chrome and black finishes, on cylindrical or square-shaped bars.

Concealed Valve

Concealed shower valves are for those who want the ultimate in minimalistic design in their bathrooms with sleek and discreet style. All of the shower workings sit behind a plate fitted to the wall or behind the wall itself. Here, only the controls, riser and showerhead are on display, meaning less bulk on the wall.

Exposed Valve

Exposed shower valves add a classy and designer-inspired look to your bathroom where all of the controls and shower workings sit externally on the wall. This allows you to switch between two water outlets, for example, such as an overhead shower and a shower handset. If you have a larger bathroom, this valve can help fill in wall space.

Traditional Valve

Traditional shower valves bring a classical design to your bathroom for a combination of new technology and all the beauty of old styling. Including level and cross handles, these valves are a combination of bar and exposed valve designs. The perfect combination of modern showering with vintage touches.

How to fit a thermostatic shower

No matter where your starting point is - you may already have a mixer shower and separate pipes for a shower - you will need to turn off your stopcock to isolate the water supply and drain the water from your pipes.

Decide where to take your hot and cold water from

If you are fitting the thermostatic shower above a bath, then you will be able to tap - or tee - into the tap water supplies. However, if you are installing a thermostatic shower in a shower cubicle or enclosure, you can tee into the nearest piping, which is often under the floorboards.

Run the hot and cold water pipes towards the shower

Once you’ve tapped into the water supply and turned off the water, you’ll need to run the pipework toward the shower. Make sure you check your thermostatic valve instructions to ensure the hot and cold water supplies are on the correct sides. Hot is usually on the left.

Plastic piping can be easier to work with and may be run under your floorboards and up behind stud walls. To prevent plastic pipes from deforming through use or heat, use pipe inserts at any joints.

Include a shut-off valve on your hot and cold pipes as close to the shower as possible. It can be easier to tighten compression joints on copper piping than plastic, so try inserting some copper pipe at the end of the plastic.

Switch the water supply back on to check for any possible leaks and put plastic pipe covers - or stop ends - over the ends of the piping.

Flush the piping

Thermostatic shower valves can be damaged by any dirt that is in the water flowing through it, so you should flush your new pipework. You can do it while checking for any leaks. Remove the stop ends from your pipes and run water through them. Hold a bucket underneath the pipes to catch any dirt.

Switch the water supply off via your stopcock once you’re done.

Mark & cut your pipes

Get your thermostatic valve and hold it next to your outlet pipes flat against the wall. Then, with a pencil, mark the amount of pipe - hot and cold - that’s needed to allow the valve to sit flush against the shower wall.

Once you’ve done this, cut the excess piping. You can use a saw or a tubing/pipe cutter.


After you’ve cut your pipes, you can drill the holes to attach the thermostatic valve. Mark where the valve will sit and the screw points, and then you drill the holes - a diamond-tipped drill head will work best on walls and tiles.

Fit a compression olive

To ensure a water-tight seal in the thermostatic valve, place a compression olive - sometimes called a collapsible olive - in each valve inlet and secure it in position by screwing the retaining nut with one turn.

Align the thermostatic valve

Now for the main event of attaching the thermostatic valve. Align the valve with the hot and cold pipes. Then, make sure they fully slide into the pipes. Now, screw your shower valve onto the wall and tighten the retaining nuts- this is best done with an adjustable spanner. 

Turn the water supply back on via the stopcock to check for any possible leaks at the inlet.

Fit the rest of your shower

Once the valve is fitted, you can install the rest of your shower - including the riser pipe or hose, and your shower head or handset.

A flexible shower hose may be easier as all you need to do is connect it to the valve via screwing it in and fit the bracket which will hold your handset.

For a fixed riser pipe, it may be supplied oversized to suit various bathroom heights, so you may need to cut it down to size. First, measure the depth of the recess that the pipe will sit in on the thermostatic valve. Then, do the same on the bracket that will secure the top of the riser pipe.

With some double-sided sticky tape, put it on the top bracket at the height you want it to be above the valve. Next, measure between the bottom of the bracket and the top mounting nut on your thermostatic valve. Add this measurement to the ones you’ve already made and cut the pipe to this length.

When cutting a riser pipe, do not use a saw - a pipe cutter is best and will provide a clean cut.

Test that the riser pipe fits based on your measurements and that it is vertical with a spirit level. If it is, mark the top bracket mounting holes, drill them, and then plug them. You can now fit the riser pipe - tightening the nuts, where necessary - then, fit and screw on your shower head.

Turn the water back on and check for any leaks. Check the thermostatic valve works by making sure the shower temperature remains constant.

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