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TMV testing requirements: service intervals, temperatures and records

Thermostatic mixing valves protect vulnerable people from scalding while stored hot water stays hot enough to control Legionella. That balance only holds if every valve is tested on time and the results are recorded.

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Last reviewed: September 2026 · General information, not legal advice — check AS 4032.3, the manufacturer's instructions and any state health requirements.

Why TMVs exist

A hot water system has two jobs that pull in opposite directions. Hot water is stored at 60°C or above to control Legionella — but water that hot, straight out of a tap or shower, is a scalding risk, especially for the very young, the elderly and people who can't react quickly.

A thermostatic mixing valve, or TMV, solves that. It mixes the stored hot water down to a safe outlet temperature: typically 45°C in healthcare and aged care settings, and 50°C in most other buildings. The storage stays hot enough for Legionella control, and the outlet stays safe for the person using it.

That's why TMVs are so common in hospitals, aged care homes, childcare centres and commercial buildings — and why a valve that drifts out of adjustment or fails matters. A TMV that isn't working properly can't be relied on to protect anyone.

Annual testing (minor service)

Under AS 4032.3, TMVs are field-tested at intervals of not more than 12 months. This field test is often called the minor service.

"Not more than 12 months" is a maximum, not a target. If a valve was tested late last year, the next test is still due within 12 months of that one. Across a building with dozens of valves, installed and serviced at different times, it's easy for a few to slip past their date unless each valve is tracked on its own.

It helps to plan the year around the valves rather than the building. Grouping valves that fall due in the same month into a single visit keeps travel down and makes it less likely that one valve in a far corner of a site is forgotten. When a valve fails its test, the repair and the follow-up result belong on the same record, so anyone looking later can see the whole story in one place.

Five-yearly major service

The major service goes further. Thermostatic actuators, and dynamic O-rings and seals, are replaced at intervals not exceeding 5 years, or sooner if the manufacturer requires.

That last part is important. Always check the manufacturer's instructions for the specific valve, because the manufacturer can set a shorter interval than the standard. The five-yearly cycle also runs alongside the annual test, so each valve effectively has two due dates to watch: its next field test and its next major service.

Records

A record of test results and repairs is kept in line with AS 4032.3 Appendix B. Those records are what show a valve has been tested on time and what was done when it wasn't performing.

For facilities in healthcare, aged care and childcare in particular, the facilities manager will often need to produce these records. The plumber who did the work is usually the one who created them, so clear, consistent records per valve make everyone's job easier.

Good records also protect the contractor. If a question is ever raised about a particular outlet, a dated result, the technician's name and a photo of the valve answer it far better than a memory of the visit. Keep the records somewhere the whole team can reach, not only on the technician who was on site that day.

A note on licensing in Queensland

In Queensland, plumbers who service and test TMVs must hold an endorsement. If you're working in Queensland or sending technicians there, make sure the people doing TMV work hold it.

Managing a valve register across many sites

None of the following is a requirement set out above — it's good practice for contractors looking after TMVs across multiple buildings:

  • One entry per valve — with its location in the building clear enough that any technician can find it.
  • Both due dates on every valve — the next field test and the next major service, so neither is missed.
  • The make and model — so you can check the manufacturer's instructions and any shorter service interval.
  • Results for every visit — outlet temperatures, pass or fail, and any adjustment made.
  • Repairs linked to the valve — what was replaced and when, especially at the major service.
  • Photos — of the valve and its label, which help the next technician and settle questions later.

With a register like this, every site becomes the same routine: the valves due this visit are known in advance, and the records are ready when the facilities manager asks.

Managing a TMV register in FieldOp

In FieldOp, each valve sits on the site's asset register with its own service history, so both the annual test and the five-yearly major service are tracked per valve. A PPM contract generates the visits automatically across every site, so nothing relies on someone remembering which valves are due.

On site, technicians record temperatures, pass or fail results and photos. Facilities managers get a branded report link they can open without an account. See how it fits plumbing work on the commercial plumbing software page.

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