Category Archives: Cylinder Valves

Cylinder Valves

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

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.

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.

Blowing up a hot water cylinder

I made this GIF from an experiment done by Myth Busters to show the extent of damage a hot water cylinder can do when there is no pressure relief. blowing-up-hwc

The image above reinforces the importance of using individuals that understand the physics of hot water and the effects an installation can have on its surroundings.

So at what point will a cylinder explode?

In principal it’s simple to understand. Heating a substance causes molecules to speed up and spread slightly further apart, occupying a larger volume that results in a decrease in density. So “larger volume” means “more space” which is limited to the size of the hot water cylinder.

If hot water is not used and your thermostat fails, your immersion element will continue heating your water (to boiling point) until such time one of the pressure relief valves activates and relieves the pressure. Every installation should include two relief valves, one on the cold water side and one on the hot water side.

This regulation was put in place around 1997 meaning that any cylinders installed prior to that may only have one source of pressure relief. Hence the low pressure vent copper pipe going through the roof.

This is where it gets tricky. Many installers dont bother replacing older valves when replacing an old hot water cylinder with a new one. Others have managed to install a tempering valve on a low pressure system right into the overflow pipe, blocking the only means of pressure relief. The hot water system then becomes a time bomb which may result in something pictured above.

Sometimes its not the plumbers’ fault but rather the homeowner who sees a pipe dripping on the outside of a house and thinks.. “Oh, this should not be leaking” and decides to “blank” it off by any means available, creating the perfect conditions for a catastrophe. My recommendation on this is, see a dripping pipe? Please call the plumber.

If you are unsure about what valves you need or already have, send us an email or give us a call for help.

 

Cold Water Expansion Valves, Also Called Energy Saving Valves

Very often we get clients calling us saying there is a pipe that is constantly dripping outside their house and they want it fixed so that it stops. The first thing that we do Is try to educate the clients on what the role of this valve is along with the rest of the valves on the hot water cylinder. So what does a Cold Water Expansion valve do?

When your cylinder is filling up with cold water at a high pressure after; let’s say you have had a hot shower, the element comes on to heat the water back up to its pre-set maximum temperature of around 60 degrees Celsius.

The water being heated causes molecules to expand and increase pressure exponentially in an already high pressure hot water system exceeding normal operating pressure.

The Cold Water Expansion has 2 roles in this situation,

  1. it’s a safety mechanism that releases excess pressure from your hot water cylinder as it heats up to avoid over pressurizing protecting the system as a primary means of release. The secondary means of release is the TPR valve which activates when the CWEV does no longer copes.
  2. Whilst this valve acts as a pressure relieve valve, Its primary role is power energy saving. It is installed on the cold line, typically close to where the cold water enters the cylinder. The pressure relief is set below the primary relief (in KPA) allowing it to drip cold water instead of hot water when expansion occurs before the other valves at the top of your cylinder (TPR valve). By doing so, it reduces hot water waste and results in a lower energy bill.

On hot days with low hot water consumption, the cold water expansion valve can run up to 10 liters per hour! Remember, that by doing so you are saving on power. The alternative would be, less water wastage at a higher pressure via the TPR valve but a higher power bill. The logic is, water is cheaper than power.

Whilst the valve is designed to drip while the cylinder is heating, if yours is dripping excessively and you believe this is not normal, it may indicate it’s time get us in to replace the valve or investigate other issues that may be forcing the valve to drip.

How do I know my cold water expansion valve is working?

Check that the valve on-top of your cylinder (TPR) is not discharging any water because if it is then the cold water expansion valve isn’t doing its job. Also, if you manually turn on the cold water expansion valve to discharge water (turn blue knob) look for discoloration of the water as this indicates the valve is rusted internally or the rubber seal has perished and is no longer effective.

Why not book in a hot water cylinder service to do a full system check? Call us today.

 

Cold_water_expansion_valves