Category: Cylinder Valves

Cylinder Valves

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Common Cold Water Expansion Problems. Leaky Hot Water Cylinder Valve.

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.

Preventative measures

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When Pressure Relief Valves Leak And What To Do

Recently there have been several claims against ‘leaking’ TPR valves. Upon testing it has been found that the relief valve is neither passing nor failing to reseat, the ‘leak’ appears to be water passing out of the blow-out cage which has opened when the easing lever has been operated too quickly during maintenance.

THE EASING LEVER SHOULD BE OPERATED SLOWLY

The purpose of the blow-out cage is to act as a ‘back-up’ relief valve which may (in certain circumstances) open when a high flow rate is passing through the TPR valve during emergency relief conditions and is normal.

Incorrectly sized or partially blocked relief drains causing back pressure may also cause the blow-out cage to activate again releasing water at the cylinder. The relief pressure of the blow-out cage is roughly 50% of the pressure rating of the TPR valve.

This new plastic device is manually resettable as opposed to the previous model which had a ‘one shot’ non-resettable metallic mechanism.

To reset the blow-out mechanism please follow the instructions belo

  1. (Fig 1) Once the water flow has ceased to turn the blow-out cage anti-clockwise to remove the device from the TPR valve body.
  2. (Fig 2) Push the valve stem back through the cage until both the stem and the washer are completely removed from the cage (a resonable amount of force will be required to push the bevelled end of the shaft through cage, lubricating oil will prevent the rubber washer from being pinched).
  3. (Fig 3) Fit the washer onto the stem and insert fully into the cage until the bevelled end ‘clicks’ back into position.
  4. (Fig 4) Fit the device into the TPR valve body and SLOWLY re-test the valve.

leaking_tpr_valves

One thing to note is that sometimes there may be a case where the valve can be genuinely faulty. Depending on age the valve may or may not be under warranty. In such cases, give us a call to book an inspection in.

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The New Rinnai TPR Valve Insulation Kit

After substantial market demand, Rinnai is pleased to announce that they have released a temperature and pressure release valve (TPR) insulation solution which is now available as a kit. This is suitable for use with all variants of Rinnai indoor mains pressure hot water cylinders.

rinnai_tpr_valve_insulation_kitA TPR valve can get very hot; almost as hot as the hot water cylinder it is fitted to. The resulting heat loss and energy consumption from this can be significant, and greatly reduces the energy efficiency of the hot water cylinder. To solve this issue Rinnai has come up with a unique TPR insulation solution.

The insulation is made from closed cell neoprene and reduces heat loss by up to 150W of energy over a 24-hour period. It is made of highly durable material and is one size fits all. The insulation kit comes pre-cut and is very simple to install. View installation instructions here.

This kit comes prepacked with selected Rinnai mains pressure cylinders. This TPR kit also allows you to retrofit it onto existing cylinders, so you can take advantage of this even if you already have your cylinder installed.

You can find this kit on our website here.