WaterTight
Dashboard
Back to Procedures
TMV Servicing

TMV Servicing

TMV Servicing

Purpose

To service mixer valves so they keep water at a safe temperature and the failsafe works properly. This stops people getting scalded.

Required Equipment

TMV service kit (cartridge, check valves, O-rings), replacement strainers, PTFE tape

Required PPE

Gloves, safety goggles, overalls

Required Tools

Spanners, screwdrivers, descaling solution, wire brush, thermometer

Step-by-Step Method

  1. Turn off both the hot and cold water to the valve.
  2. Open the tap to release pressure and drain water.
  3. Take off the valve cover.
  4. Remove and clean the strainers (they catch dirt).
  5. Remove and check the one-way valves (check valves). Replace if worn or scaled.
  6. Check the temperature part (cartridge). Replace if damaged or if it is due.
  7. Clean everything. Descale if needed.
  8. Put it back together with new seals.
  9. Turn the water back on. Wait 2-3 minutes.
  10. Set the mixed water temperature to 41 degrees C max.
  11. Test the failsafe: Turn off the cold water only. The hot water must stop within 2 seconds. If it does not, replace the cartridge and test again.
  12. Write down the temperatures, failsafe result, and parts replaced.

Pass Criteria

Mixed water is 41 degrees C or below and steady. Failsafe works (hot water stops within 2 seconds of turning off cold). Strainers are clean. No leaks.

Fail Criteria

Mixed water is above 41 degrees C. Failsafe does not work (hot water keeps running when cold is off). Leaks. Strainers blocked.

Common Problems & Corrections

Temperature drifts - Replace the cartridge. No failsafe - Replace cartridge; check for dirt stopping the valve closing. Low flow - Clean or replace blocked strainers and check valves. Temperature goes up and down - Check pressure difference between hot and cold; check one-way valves. Scaling - Descale; think about water treatment if it keeps happening.

Warnings

Hot water at 60 degrees C causes third-degree burns in 3 seconds. Always test the failsafe after servicing. Never leave a valve in service with a broken failsafe. Turn off water before opening the valve.

Relevant Legislation

ACOP L8 (4th Edition), HSG274 Part 2 (annual service), BS EN 1111 / BS EN 1287, NHS D08 (TMV3 in healthcare)