What does a temperature pressure relief valve do?
Temperature pressure relief (TPR) valves (also known as a pressure relief valve or PRV) are fitted to all mains pressure storage hot water tanks. They are a brass valve found near the top of the system and have a small lever or ring-pull on them.
Heat causes expansion of water which increases pressure and a TPR valve is designed to open and purge water from the hot water storage tank to reduce the internal water pressure of the tank.
If a thermostat fails and the water in the tank continually heats, the relief valve will open to purge the high temperature hot water.
In essence, it quite literally stops your hot water system becoming a bomb, as too much pressure and temperature in the system will split the tank and may cause it to burst with tremendous force.
When the internal temperature or pressure reaches the maximum allowable working pressure or 99⁰C in temperature, a functioning TPR valve will open and expel hot water out of the tank, allowing for cooler water to enter the tank and reducing the internal pressure.
How do I know if my temperature pressure relief valve is working?
A working TPR valve will drip during a heating cycle and if you notice this happening (especially after someone has used hot water), you probably don’t need to worry. A functioning TPR valve can drip up to 3% of the tank’s capacity in a 24-hour period.
What it shouldn’t do is drip constantly, all day, every day or have water running from it like a tap. If you open the lever or ring-pull, pressurised hot water should flow from the relief valve drain.
If your temperature pressure relief valve is running water or won’t release water when opened, it’s time to call a plumber.
How 6 Star Hot Water & Plumbing can help with temperature pressure relief valves
We recommend replacing your TPR valve every 5 years to ensure proper function. This can be done as part of our recommended 5-Year hot water servicing. We also recommend purging some water from the system every 6 months. To do this, simply pull and hold the small lever or ring-pull for about 30 seconds. This will both make sure the internal mechanism hasn’t seized and will also flush debris or any nesting insects from the drain line.
If you notice your temperature pressure relief valve running or haven’t had it replaced in a few years, call us on 0448844911 for expert advice in the Canberra and Queanbeyan area.
Temperature pressure relief valves for Dux, Rheem, Thermann, Vulcan and most brands
Most hot water brands come packaged with a specific pressure rated TPR valve and will also have the pressure rating listed on the compliance plate. This rating must be adhered to and can only be replaced by a valve with the same pressure rating or lower. These valves come in 700kPa, 850kPa, 1,000kPa and 1,400kPa.
Stiebel Eltron temperature pressure relief valves are the exception
Stiebel Eltron heat pumps are packaged with a 700kPa TPR valve. Most of Canberra’s water pressure sits around 500kPa, but with fluctuations in water pressure, we have noticed this has led to a fairly common occurrence of leaking Stiebel Eltron systems. Stiebel Eltron has assured us that it is safe to install an 850kPa TPR valve if the water pressure is too high, but this can lead to leaks around the system’s heating element.
Hot water system temperature and pressure relief valves we replace:
Please note, TPR valves cannot be repaired.
- Apricus – temperature and pressure relief valves
- Aquamax – temperature and pressure relief valves
- Beasley Typically not required as they have an open vent at the top
- Chromagen – temperature and pressure relief valves
- Conergy – temperature and pressure relief valves
- Dux – temperature and pressure relief valves
- Edwards – temperature and pressure relief valves
- Everhot – temperature and pressure relief valves
- EvoHeat – temperature and pressure relief valves
- Hills – temperature and pressure relief valves
- iStore – temperature and pressure relief valves
- Kelvinator – temperature and pressure relief valves
- Quantum – temperature and pressure relief valves
- Reclaim – temperature and pressure relief valves
- Rheem – temperature and pressure relief valves
- Rinnai – temperature and pressure relief valves
- Solahart – temperature and pressure relief valves
- SolarArk – temperature and pressure relief valves
- Stiebel Eltron – temperature and pressure relief valves
- Thermann – temperature and pressure relief valves
- Vulcan – temperature and pressure relief valves
What causes the hot water relief valve to open?
A pressure relief valve is designed to open and expel hot water if the internal tank pressure is too high or if the internal temperature reaches 99⁰C.
How do I know if my hot water relief valve is bad?
A hot water relief valve will drip during a heating cycle under normal conditions. A faulty pressure relief valve will not expel any water when you pull the lever, or will run constantly like a tap.