A tempering valve is required for almost every new or replacement hot water system in WA. Here is when you need one, what it costs, and how to tell if yours is failing.
Do I Need a Tempering Valve in WA?
Yes. A tempering valve is legally required in Western Australia for almost all new and replacement hot water systems that supply sanitary fixtures such as bathrooms and showers.
The reason comes down to two facts that pull against each other. Your tank has to store water at a minimum of 60°C to stop Legionella bacteria growing in it, and water at that temperature is hot enough to cause serious burns in seconds.
A tempering valve resolves the conflict by capping what actually reaches the tap at a safe 50°C.
When Is a Tempering Valve Required in WA?
The rules are triggered by work being done, not by the calendar.
That distinction matters, and it is where most of the confusion sits.
When You Do Need One
A tempering valve is mandatory in these situations:
- All new residential builds
- Bathroom renovations and other major plumbing work
- Any time an existing hot water unit is replaced
- When a system is upgraded in capacity
- When you change fuel type, such as moving from gas to electric or across to a heat pump
If you are planning bathroom or laundry renovations, or working out the cost of a hot water system replacement, assume the valve is part of the scope.
When You Do Not
- Existing homes are not required to retrofit a tempering valve, provided the system is not being replaced
- Systems serving only non-sanitary fixtures are exempt
- Dedicated kitchen sink and laundry taps do not strictly require tempered water
So if you have an older system running happily without one, you are not breaking any rules.
The obligation arrives the day that system is replaced.
Replacing Your Hot Water System?
We fit and certify a tempering valve as part of every hot water installation we do, quoted within one fixed price for the whole job rather than as a surprise line item.
How Long Tempering Valves Last and How to Spot One Failing
A tempering valve typically lasts 5 to 8 years with maintenance. In Perth, expect the shorter end of that.
Perth water quality is hard, and dissolved minerals leave sediment inside the valve body over time. That build-up gradually stops the thermostatic element responding properly to temperature setting changes, which is how a valve fails. Regular servicing clears it first, and it is the cheapest maintenance you will do on a hot water heater.
Signs yours is on the way out:
- Water temperature fluctuating at the tap for no obvious reason
- A hot tap suddenly running scalding hot
- Water never reaching a properly hot temperature
- Temperature swinging when someone uses another outlet
Annual testing is recommended in WA and takes very little time. A failed tempering valve is a safety problem rather than a comfort one.
By the time you notice water running scalding hot, the device protecting your household has already stopped working.
Tempering Valve or Thermostatic Mixing Valve?
Standard tempering valves are what goes on a normal domestic home. They blend hot and cold water reliably and hold the outlet within an acceptable range.
Thermostatic mixing valves, usually shortened to TMVs, do the same job with even more precise control and a faster shut-off if the cold water supply fails. They are used in hospitals, aged care facilities and similar settings, where the people using the water are least able to react to a sudden temperature change.
For a standard Perth house, a tempering valve is the correct valve. You do not need a TMV, and anyone recommending one for an ordinary home should be able to explain why.
How Much Does Tempering Valve Installation Cost in WA?
A hot water tempering valve itself runs roughly $120 to $180 retail. A professional tempering valve installation or replacement, including labour, typically lands between $280 and $420, and the work usually takes one to two hours. Annual testing generally costs somewhere around $80 to $120.
Here is the context that matters more than those figures. When you install a tempering valve as part of a new hot water system, it is normally quoted within the whole job rather than billed separately, so you see one fixed price rather than a surprise line item.
If a changeover quote makes no mention of a tempering valve, ask. On a replacement it is required, so either it is included and unstated, or something has been missed.
These are indicative ranges. The accurate number comes from a quote on your property, because access and the existing setup change the labour.
Getting a Tempering Valve Installed in Perth
We fit and certify tempering valves as part of every hot water system installation and replacement we do, across gas hot water systems, storage hot water systems, solar hot water systems and heat pump units alike.
We also service and test existing valves, and replace them when they fail. Proper installation matters on a safety device. We hold plumbing licence PL 9874 and gas licence GF 014602, so the work certifies first time.
If your current system has no tempering valve and you are not replacing it, we will tell you straight rather than selling you work the rules do not require.
Still Contemplating Whether or not You Need a Tempering Valve? Reach out to Proud Plumbing & Gas!
The rule is simpler than it sounds. If you’re replacing a hot water system, renovating a bathroom or building new, a tempering valve is required. If your existing system is staying put, it isn’t.
Where it’s worth a call is the grey area in between, or if your hot water has started running scalding or swinging in temperature. That’s a valve failing, and it’s a safety issue rather than a nuisance.
We fit and certify tempering valves as part of every hot water installation we do, and we service, test and replace existing ones.
Get in touch and we’ll tell you what your situation actually requires, including if the answer is nothing.
