Do you have a mains pressure hot water cylinder? Is the overflow constantly draining? Or the relief valve leaking water? In other words, do you have a pipe sticking outside the house maybe going into a gully/ drain that is always dripping water? If so, it will be an issue with one or both of your relief valves.
What is a relief valve?
A relief valve is the most important part of the mains pressure hot water system, it protects the tank from over pressurizing. When hot water is used and the element or gas fire starts up to begin the reheating process, the heat increases, and so does the pressure. In order to prevent the tank from bursting, the excess pressure caused by heat needs to be removed from the tank. This is where relief valves come into play. The relief valve will open when specific conditions are met, which is usually when the pressure increases to a point which the valve is designed to open or if the temperature increases too much
Cold Water Expansion Valve (CWE) does all the day to day reliving of pressure, the valve is fitted to the cold water inlet of the cylinder. The CWE is the first valve to relief pressure on a mains pressure system, it will be set to relieve at a lower pressure setting when compared to the TPR valve, they are designed to be the first to relieve because they are fitted to the cold water inlet, this means all the day to day relieving of pressure is through cold water, and not hot water, this in turn will save you money on power as it will not be wasting hot water.
Temperature Pressure Relief (TPR) is designed to be a secondary back up if the cold-water expansion valve fails but also relives water in the event of overheating. If your system is fitted with a cold water expansion valve, and the TPR is dripping water, that will mean there is an issue with the TPR valve and should be replaced.
Check out one of our older blogs to find out more about cold water expansion valves here and the benefits of having one if you do not have one already.
Importance of maintaining relief valves
There are several things that can cause issues with relief valves, and if regular maintenance is not performed, you could be left with higher water bills, higher power bills and even a flooded house in extreme cases. For this demonstration we have cut an RMC Cold Water Expansion valve in half to help show the way the valve works.
Continuous water dripping through overflow or relief drain
Debris or sediment, If you live in an area with lots of building and road works going on, or even if you have an old style water main that may be falling apart internally, this can cause large amounts of debris to make its way into your homes water supply, this debris gets stuck in seal of the relief valve will cause the valve to never be able to shut properly, this will cause a continuous flow of water, this is an issue that should be addressed immediately as the continuous flow of water through the valve will cause holes in the brass and can even cause the water to spray from the brass of the valve itself causing a flood inside the house, in some cases you may be able to avoid the need to call a plumber by simply flushing the valve on a regular basis (recommended every 6 months) otherwise the valve may just need a good clean to repair the issue.
Old, expired cartridge, with age the rubber will become brittle and will start to deteriorate, in some cases you are able to simply replace the cartridge, like with the RMC Cold Water Expansion valve, which is easily, and inexpensively replaceable, other causes could be that the return spring has lost its “springiness”, so it is not able to fight the pressure to close again properly
Hard water conditions, sometimes the water supply you get is not ideal, it may contain things that could corrode these valves or even appliances using the water in a short amount of time. If you believe this may be your issue, we recommend getting your water quality tested to ensure.