Hot Water Expansion Control Valve

March 21, 2014 12:30 am Published by
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Do we need an Expansion Control Valve and what is it?

In many areas of Australia the water quality differs. South Australia, Western Australia and other areas where scaling water are present, a Expansion Control Valve is fitted to the cold water main supply line to the hot water heater unit. The Expansion Control Valve may discharge a small quantity of water from its drain during the heating period instead of the Pressure Temperature Relief Valve on the hot water heater.
The expansion control valve should be checked for its performance at the regular service intervals of your hot water unit. The valve should be replaced at intervals not exceeding 5 years as recommended by the manufacturer. The valve may need to be replaced more frequently in areas where there is a high incidence of water deposits due to the water chemistry or older rusted galvanised pipe work.

There are many factors that can effect your hot water unit cylinder and associated valves life span. One factor is the changing or alternating from one water supply to another can have a detrimental effect on the operation and life expectation of the water storage cylinder, pressure temperature relief valve and heating unit. Where there is a change over from one water supply to another such as a rainwater tank supply, bore water supply, desalinated water supply, public reticulated water supply or water brought in from another supply, then the water chemistry information should be sought from the supplier or it should be tested to ensure the water supply meets the

requirements recommended by the hot water service manufacturer.

The most common modern hot water service units are manufactured to suit the water conditions of most public reticulated water supplies. However, there are some known water chemistries which can have a detrimental effect on the water heater cylinder and heating unit. If you are unsure of your water chemistry, you may be able to obtain this type of information from your local water supply authority. It is recommended that your water heater should only be connected to a water supply which complies with the manufactures guidelines.
Your licensed plumber will be aware of any such local water conditions and will be able to advise you on any precautions and the installation of any appropriate valves.

Scaling water is water that contains levels of calcium carbonate < total hardness in excess of 200mg/Litre at any time when the water heater is operating >. Scaling water can block and prevent the pressure and temperature relief valve from operating, resulting in damage to the water storage cylinder and water heater components.
An expansion control valve is mandatory in South Australia and Western Australia and must be fitted in ALL areas with scaling water to prevent blockages of the pressure and temperature relief valve.

Failure to install an expansion control valve where scaling water conditions occurs may result in the water storage heater cylinder failing, or under certain circumstances, exploding.
For an absolute demonstration of these circumstances go to our website and view two videos about this topic on our hot water page…

To avoid damage to the storage cylinder and water heater components, manufactures strongly recommend scaling water be treated before entering the hot water heater by fitting appropriate water filters and conditioners etc. Once again you can contact you local authority and licensed plumber for information on water in your area. A build up of white sediment on hot water taps or shower roses can be an indication of scaling water.

Expansion Control Valve Running
If an expansion control valve is fitted in the cold water supply line to the water heater, it may discharge
a small quantity of water instead of the hot water heaters pressure temperature relief valve. This has the benefit of conserving energy as the discharged water is cooler.
In some areas, local regulations may make it mandatory to install an expansion control valve in the cold water line to the hot water heater. The expansion control valve must always be installed after the non return control valve and be the last valve installed prior to the hot water heater. If your control valve is continually running contact your local licensed plumber as this is a sign that your hot water unit is due for a service.

When was the last time your hot water unit was serviced?

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