How to Install a Thermostatic Mixer Shower

Our expert guide on how to install a thermostatic mixer shower will help you complete your bathroom renovation project. The guide is broken down into easy to follow steps, and there’s some handy tips to make the job easier, plus we’ve listed all the tools you’ll need to get the job done with a minimum of fuss.

What is a thermostatic mixer shower?

Mains-fed showers can be an issue – flushing the toilet or running a hot tap elsewhere in your home can make your shower run freezing cold or scalding hot. If you’re looking for a new shower then you definitely need to choose a thermostatic mixer shower to ensure a safe and comfortable showering experience. This type of shower allows you to pre-set the temperature to what you’re comfortable with and then maintain that temperature regardless if someone flushes the loo or turns on a tap.

Is a thermostatic mixer shower compatible with my water system?

Our thermostatic showers are suitable for use with pumped systems, gravity, standard mains pressure and combination boilers. It’s a good idea to check with the supplier that the shower you want is compatible with your water system before purchasing.

Types of thermostatic mixer showers

Thermostatic mixer shower valves are available in two styles – exposed or concealed.

Concealed shower valves just have the controls on show with the valve and water connections hidden behind a plate. This guide explains how to fit an exposed shower, but the principle is the same for a concealed valve.

An exposed shower valve attaches to the face of the wall, and the hot and cold pipes either run up the wall to fix underneath the unit, or come through the wall to attach to the back.

traditional shower kit with concealed thermostatic shower valve

Concealed thermostatic shower valve

traditional shower system

Exposed thermostatic shower valve

Installing your thermostatic shower

Tools required:

  • Pipe cutters for plastic and copper pipe
  • Pencil
  • Tape measure
  • Adjustable spanner
  • Tile drill
  • Spirit level
  • Dust sheet
  • Thermostatic mixer shower
  • Shower head
  • 15mm plastic and copper pipe
  • Plastic and copper connections – tees and elbows
  • Shut-off valves
  • Double sided tape

1. Decide where to take the hot and water supplies from

First you’ll need to decide where to take the hot and cold water supplies from. If you are fitting the shower above the bath you can tee into the tap supplies. If you are fitting the thermostatic shower valve into a shower enclosure you can tee into the closest hot and cold pipes, which are often found under floorboards or hidden in a cupboard. You can check which is which by tracing the pipes back from the nearest hot and cold taps. The flow of water can be felt through the pipe with the tap running. Run each tap in turn, you’ll know which the hot water pipe is as it warms up quickly.

2. Isolate the supply

Once you’ve decided where to take the hot and cold water supplies from you can start the work, but before doing anything you’ll need to isolate the supply. So, switch off the stopcock (usually positioned under the sink) and then open the hot and cold taps to drain away the water in the pipes.

3. Run the pipework towards the shower

When you’ve isolated the supply, tee into the hot and cold supplies and run the pipework towards the shower. Check the instructions that are included with the valve and feed the hot and cold supplies to the correct sides – hot is on the left and cold is on the right.

Top tip: for a hassle-free plumbing solution, plastic pipe can be run under floorboards and up behind stud walls. To prevent plastic pipe from deforming use pipe inserts at any joints.

Include a shut-off valve on the hot and cold supplies as close as possible to the shower. It’s easier to tighten up compression-type joints on a copper pipe, so slot in a section of copper pipe at the end of the plastic pipe runs. Once you’ve done this, put the plastic stop ends on these pipes, switch the stopcock back on and check for leaks on the new pipe runs.

4. Flush the pipework through to remove any dirt

To prevent any damage to the shower valve, flush the new pipework through to ensure any dirt flowing in the water is removed. Turn the water off, remove the stop ends and get someone to hold a bucket under the outlets while you turn the water back on. When you have finished flushing the water through you can switch off the stopcock.

5. Work out how much outlet pipe is required

Take the shower valve, place it against the wall where it’s going to be fitted and mark off the amount of outlet pipe required to allow it to fit flush to the wall.

6. Cut the outlet pipes

Next, cut both outlet pipes to the required length.

Top tip: use a close quarter tubing cutter, which is great for tight spaces.

7. Drill the holes

You can now mark and drill the holes for the valve. Use a diamond- tipped tile drill if you’re drilling into tiles.

Top tip: to create perfect holes fast use a water-cooled drill guide.

8. Place a collapsible olive into each inlet

Place a collapsible olive into each inlet on the valve and secure by screwing the retaining nut on by one turn.

9. Align the valve with the supply pipes

Align the thermostatic valve with the supply pipes ensuring they slide into the inlet pipes fully. Next, screw the shower valve to the wall and tighten the retaining nuts with an adjustable spanner. Turn the stopcock back on (make sure the shower valve is turned off first) and check for leaks at the inlet pipes.

10. Fit the rest of the shower kit

The flow of hot and cold water from an exposed shower valve is taken to the shower head by a flexible hose or a solid riser pipe. (For a concealed shower valve it may be taken to a wall or ceiling mounted fixed shower head).

If your shower kit uses a flexible hose all you need to do now is connect it up and fit the bracket that holds the handset in place.

If you have a riser pipe it may need to be cut to length first to suit your ceiling height. If you do need to cut it down, measure the depth of the recess that the pipe sits in on the valve and then on the bracket that secures the top of the riser.

11. Take measurements

Take some double-sided tape and put it on the top bracket, stick it at the height you want it to be above the shower valve. Measure between the bottom of the bracket and the top mounting nut on the valve. Add this measurement to those you made in the previous step and cut the riser pipe to this length.

Top tip: make sure to cut the pipe with a pipe cutter, not a hacksaw.

12. Test the riser pipe fits

Test that the riser pipe fits between the valve and bracket, and ensure it’s vertical with a spirit level. Mark off the top bracket mounting holes, drill and plug.

13. Fully fit the riser pipe

Now you can fully fit the riser and tighten the top and bottom nuts. Some shower kits have an extension piece that attaches to the riser’s top bracket – this takes the shower head. Fit this and screw the shower head on. Check for leaks by running the shower. Ensure the thermostat works by switching on the taps and make sure the shower temperature remains constant.

Expert Tips

A Plumber’s Tip

“Be very careful when hammering in the wall plugs. It’s a good idea to use a suitable hammer – otherwise, you run the risk of swinging and smashing into a tile instead. In fact, hammer the wall plugs directly into the wall behind, if possible. This will tighten the screw into the brick surrounding the drill hole without cracking the tile.”

Homecure Plumbers, central heating and boiler services based in London – Visit Website

DIY is a great way to save time and money, however to avoid disappointment, invalidating your warranty, and potential injury we recommend hiring a trained professional. This guide is for your information only and if you do decide to be bold and try it, we cannot be responsible for any outcome.

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