If your hot water has suddenly gone icy cold or uncomfortably hot, your tempering valve could be the culprit.
This small but essential plumbing component plays a big role in your hot water system by blending hot and cold water to deliver a safe, consistent temperature to your taps and showers.
When your tempering valve is working properly, you barely notice it. But when it fails, it can lead to annoying temperature fluctuations – and even serious safety risks. Scalding water isn’t just unpleasant; it can be dangerous, especially for children and the elderly.
In this blog, we’ll explore what a tempering valve does, how to spot when it’s not working, and what to do about it. A little knowledge can go a long way toward keeping your home safe and your hot water comfortable.
What is a Tempering Valve?
A tempering valve is a safety device that regulates the temperature of your hot water.
Its main job is to mix hot water from your water heater tank with cold water from your mains supply to ensure the water coming out of your taps and shower stays at a safe temperature – typically around 50°C in most Australian homes.
This helps prevent accidental burns, which is especially important for households with children, the elderly, or anyone with sensitive skin.
Hot water has to be stored in a tank at about 60°C to prevent the growth of dangerous bacteria (such as Legionella), but this is a dangerous temperature for our skin.
The valve constantly adjusts the water mix as needed, responding to changes in water pressure or temperature. It’s usually installed near your hot water system and works automatically in the background.
If the tempering valve fails or becomes blocked, you might notice your hot water running too hot, too cold, or not at all. Keeping this valve in good shape is essential for both safety and everyday comfort.
Signs Your Tempering Valve is Failing
A tempering valve often works quietly in the background – until something goes wrong. When it starts to fail, your hot water system may show some clear warning signs.
Keep an eye (and ear) out for the following:
- Inconsistent water temperature – If your hot water keeps switching between scalding and lukewarm, the tempering valve may be stuck or malfunctioning.
- Sudden lack of hot water – A faulty valve might restrict hot water completely, leaving you with cold showers.
- Very hot water from the tap – If the valve isn’t blending in enough cold water, it could allow dangerously hot water through.
- Reduced water pressure – Blockages inside the valve can slow down your water flow.
- Visible leaks or corrosion – Damage around the valve or hot water system can also point to internal issues.
If you notice any of these signs, it’s a good idea to call a plumber promptly.
Why a Faulty Valve is a Serious Problem
When your tempering valve isn’t working properly, it’s more than just an inconvenience – it’s a potential safety hazard. The valve is designed to keep your hot water at a steady, safe temperature.
If it fails, the water coming out of your taps or shower could suddenly become scalding hot, increasing the risk of burns. This is especially dangerous for young children, elderly family members, or anyone with limited mobility or sensitivity to heat.
On the flip side, a faulty valve might allow only lukewarm water through, making showers uncomfortable and dishwashing less effective. In some cases, water that’s not hot enough can also encourage the growth of harmful bacteria (e.g. Legionella).
Beyond safety and hygiene, a malfunctioning tempering valve could mean your plumbing system is no longer compliant with Australian standards. So if you notice inconsistent water temperatures, it’s best to get it checked out sooner rather than later.
Common Causes of Valve Failure
Tempering valves are durable, but like any plumbing part, they can wear out or malfunction over time. If yours isn’t working properly, it could be due to one of these common issues:
- Age and general wear – Over time, the internal components of the valve can degrade, especially if the valve hasn’t been replaced in more than 5 years.
- Mineral or sediment build-up – Hard water can cause calcium and other minerals to build up inside the valve, blocking proper water flow.
- Incorrect installation – If the valve wasn’t installed or adjusted correctly, it may not function as it should from the start.
- Water pressure problems – Uneven or fluctuating water pressure can affect the valve’s ability to mix hot and cold water consistently.
- Thermostatic failure – The internal thermostat can become faulty, leading to poor temperature regulation.
Regular maintenance and inspections can help catch these issues early.
Should You Call a Plumber?
If your hot water suddenly turns cold or scalding, it’s natural to wonder if you can fix the tempering valve yourself.
In some cases, a basic issue like mineral build-up or a clogged filter might be cleared with a gentle clean – if you’re confident and know your way around plumbing.
But tempering valves are precise safety devices, and tinkering with them without the right knowledge can lead to more problems or even make your system unsafe.
Most of the time, it’s best to leave tempering valve issues to a licensed plumber. They can diagnose the problem, determine whether it needs a repair or full replacement, and ensure it’s adjusted correctly for your household’s needs.
Plus, a professional will make sure the work meets current plumbing regulations. So, if you’re unsure, don’t take the risk – call a plumber and get it sorted the safe and proper way.
How to Prevent Tempering Valve Issues
While tempering valves are built to last, a little care goes a long way in keeping them working properly. Here are some simple ways to avoid future problems:
- Schedule regular plumbing check-ups – A licensed plumber can inspect your tempering valve during routine maintenance to catch any early signs of wear or failure.
- Replace the valve every 5 years – Most manufacturers recommend replacement around this time to maintain safety and performance.
- Install a water filter or softener – If you have hard water, a filter can help reduce mineral build-up that clogs the valve.
- Avoid DIY tampering – Trying to adjust or repair the valve yourself can throw off its settings or damage internal parts.
- Watch for changes in water temperature – Early signs like fluctuating heat are worth investigating before bigger problems arise.
A bit of prevention now can save you from costly repairs later.
Don’t Wait for a Scalding Surprise
When your tempering valve isn’t working, it can throw your whole hot water system out of balance – making daily tasks uncomfortable or even unsafe.
From scalding showers to lukewarm dishwater, the signs are hard to ignore. But knowing what a tempering valve does, how it fails and what to watch for puts you in a much better position to act quickly. Whether it’s a simple clean or a full replacement, getting a professional plumber involved is usually the safest and smartest option.
Regular maintenance and replacing the valve every few years can also help you avoid trouble down the track.
Don’t wait for a nasty surprise – if something seems off with your hot water, it might be time to check your tempering valve and make sure everything’s working as it should. Safety, comfort and peace of mind are well worth it.
Please note: This information is provided for advice purposes only. Regulations differ from state to state, so please consult your local authorities or an industry professional before proceeding with any work. See our Terms & Conditions here.
FAQs About Tempering Valves
Do you have any questions about your tempering valve not working? If so, we’ve got answers to the most commonly asked questions right here.
If your hot water suddenly becomes too hot, too cold or keeps fluctuating, your tempering valve could be to blame. Other signs include reduced water pressure, leaks near the valve, or no hot water at all. If you notice any of these, it’s best to get a plumber to take a look.
Tempering valves are precise safety devices, and DIY fixes can do more harm than good. While you might be able to clean a blocked filter, most issues – like internal wear or thermostat failure – need a licensed plumber to repair or replace the valve safely and correctly.
Most tempering valves should be replaced every 5 years or so, depending on water quality and usage. Regular inspections can help spot problems early and ensure your valve is working properly.
