How to fit a thermostatic mixing valve

Thermostatic mixing valves prevent injury by making sure that extremely hot water (which is at that temperature to kill off germs) gets mixed with cooler water before it reaches our bath tubs and showers. They are soon (early 2010) to become a compulsory addition to pipe work in England and Wales, having been made essential in Scotland some time ago. Northern Ireland will follow suit in the near future. Here's a guide on how to fit a thermostatic mixing valve to your plumbing to stay in line with Building Regulations.

Level of difficulty

Level 3: Advanced

What you need

  • Thermostatic mixer valve
  • Sealant
  • Screws
  • Screw driver
  • Compression tee
  • Power drill
  • Saw
  • Hose
  • Rag
  • Safety goggles
  • Rust-proof screws
  • Nails
  • Tiles

The steps to follow

  1. Shut off the mains water supply.
  2. Drain the rising main via the drain-cock next to the stop tap.
  3. Cut into the pipe at the chosen point and fit a compression tee.
  4. Connect the branch pipe to the tee.
  5. Use rust-proof screws to mount the shower on the wall.
  6. Flush both hot and cold water supplies before fitting the thermostatic mixing valve. This step ensures that the water supply will be clear of debris.
  7. Attach a hose to a faucet, and feed it to the pipes.
  8. Flush the waste out of the pipe.

Mounting the thermostatic mixing valve:

  1. Mark drilling holes on the wall where you’d install the thermostatic mixing valve.
  2. Drill the holes and insert wall plugs.
  3. Fit the screws to the back plate and fasten it to the wall.
  4. Place the valve body to the wall and lock with screws.
  5. Fill the outlet adaptor to the valve.
  6. Connect the inlet pipes to the valve with the compression tee.
  7. Now connect the supply pipe to the shower inlet and run it back to the mains.

Concealing the thermostatic mixing valve mounting:

  1. Cut a hole on the wall where the hot and cold water supplies are located. This is where you'll connect the mixing valve to the hot and cold water supply.
  2. Flush both hot and cold water supply.
  3. Fasten wall fixings to the shower thermostatic control.
  4. Connect the valve to the water supplies.
  5. Tighten the threaded pipe with a wrench in the valve and tighten the screws.
  6. You can either tile up the wall and fit the shower valve faceplate on the wall or fit the plate directly onto the wall.
  7. Apply a sealant around the shower valve faceplate.

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