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Thermostatic Mixing Valve Maintenance

August 2014

In addition to supplying TMVs, we also assist with technical support with regards to TMV regulations, servicing and maintenance requirements. Whether it be over email or phone, or during one of our frequent talks during the TMV TAFE classes.

We find that the most common question regarding TMVs is the regulations for maintenance. So, we have written a brief outline below to assist with what the basic requirements are as per the Australian Standard AS4032.3; Water supply—Valves for the control of heated water supply temperatures Part 3: Requirements for field-testing, maintenance or replacement of thermostatic mixing valves, tempering valves and end-of-line temperature ccontrol devices


Caleffi TMV
  • Replacement of thermostat and o-rings every 5 years
  • Inspection and maintenance at least every 12 months as per Section B4.2 below

B4.2 Regular inspection, testing and maintenance

The procedure to be followed shall be in accordance with the manufacturer’s instructions.
The minimum activity as per AS4032 requirements shall include the following:
Please note the italicised text are the recommendations from All Valve to comply with these regulations.

  • Strainer cleanliness.
    • Use the plug on the right angle isolating / strainer valve to blow out any debris, or alternatively use a spanner to open the cap of the right angle isolating / strainers in order to remove and clean the strainer. HINT: isolate the ball valves first and connect a 1/4" John Guest type fitting and tube and run to a bucket.
  • Non-return valve operation.
    • Turn off one of the ball valves (hot or cold) and remove the 1/4" black plug from the strainer blow down port on the SAME SIDE – this will check the cross connection and integrity of the check. If no water comes out then check integrity is good. If it leaks, then fix or replace the check component. Repeat procedure with the other side. HINT: isolate both ball valves first and connect a 1/4" John Guest type fitting and tube to the 1/4" blow down port and run to a bucket.
  • Discharge temperature measured at the nearest outlet to the valve for high and low flow.
    • Use a temperature probe to check temperature at nearest outlet. If it is not holding or reaching the set temperature, then follow the trouble shooting guide below for Caleffi TMVs.
  • Test cold water shut-off operation / Test hot water shut-off operation.
    • By isolating the hot water and cold water one at a time, the TMV valve should shut down almost completely (slight flow or dripping is allowable). If a lot of water is still flowing with the hot or cold valve isolated, then the valve is compromised; see below for trouble shooting.
  • Replacement / lubrication of dynamic ‘o’ rings at intervals not exceeding 5 years
    • The Caleffi TMV has 1 dynamic o-ring which is located in the body of the valve and sits against the thermostat flow conveyor. This should be lubricated regularly (recommended at least every 12 months during inspection) and replaced every 5 years.


If the Caleffi TMV is installed as per manufacturer’s requirements and within the specified operating parameters and still not complying with above tests, then the most common issues are listed below. If the issue is not listed , you can download the instruction manual at the bottom of the page, or call us for further assistance.

If thermal shutoff fails; or not holding set temperature

  • The minimum temperature differential not achieved.
    • Increase the temperature of the hot water
  • Dynamic o-ring is leaking and not sealing against the thermostat.
    • Usually from debris or dry o-rings; clean or replace o-rings and regrease with appropriate o-ring grease.
  • Internal mechanism is being hindered by debris
    • Clean debris or scale from the valve and o-ring and regrease with appropriate o-ring grease.

Fluctuating temperatures or pressure

  • Perform thermal shutoff test integrity of the dynamic o-ring
    • If it fails, replace o-ring and regrease
  • Pressure fluctuations
    • Install pressure reducing valves in the system to stabilise pressure
  • Temperature fluctuations
    • Fix source of hot water for a stable supply
    • Valve not commissioned correctly. Check that the adjustment spindle isn't wound out to the maximum setting to achieve a temperature setting above 50 degC.
    • The Caleffi TMV is suitable for instantaneous heaters, however, sometimes in ring mains served by instantaneous systems, the circulating temperatures fluctuate too much for the TMV to provide a stable temperature. It may be necesseary to use a buffer tank in the system to help stabilise the circulating temperatures.


If you need any help; call All Valve Industries at 02 8543 9811


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