|
As a key part of the Halifax Water's Cross Connection Control Program, Halifax Water staff continually work with our customers to ensure effective operation of their water systems in conjunction with Backflow Prevention (BFP) Device installations. As part of this program we provide the following information on Thermal Expansion to help prevent any problems within your water service piping.
Thermal expansion occurs when water is heated by a hot water heater or other device. When heated, water density decreases and volume increases/expands. For example, water heated from 32ºC to a thermostat setting of 60ºC in a 150 litre hot water heater will expand by almost 2 litres. The extra volume created by this expansion sometimes overcomes the incoming supply pressure and backs out through the service line into the public water supply.
During no-flow periods in the system, Backflow Prevention Devices, Pressure Reducing Valves, and other one-way valves create a ‘closed system’, thus eliminating a path for expanded water to flow back into the public water supply.
Thermal expansion of water in a closed plumbing system can create a number of annoying and potentially dangerous problems. These include: the build-up of unusually high pressure in a system causing pressure surges an/or the chronic or continuous dripping of a temperature and pressure (T&P) relief valve. In addition, dripping faucets and leaking toilet tank ball cock fill valves are also symptomatic of thermal expansion.
More serious problems can also occur due to thermal expansion. When dangerous pressures are built up in a water heater, internal parts may fail such as the internal flues, fittings or water connections. If a flue way collapses, it can lead to the potential release of toxic gases, such as carbon monoxide into living spaces. Thermal expansion can also lead to a ruptured or distorted hot water heating tank and may void the manufacturer’s warranty.
According to the National Plumbing Code 1995 (Section 6.1.11), “When a Backflow Prevention Device, Pressure Reducing Valve, or a Check Valve is required, protection against thermal expansion may be required. To accommodate the increase in pressure caused by thermal expansion within a closed water distribution system, one of the following should be installed:
(1) a suitable sized diaphragm expansion tank designed for use within a potable water system
(2) an auxiliary thermal expansion relief valve (T.E.R. valve) conforming to CAN/CSA- B125, “Plumbing Fittings,” set at a pressure of 550 kPa or less and designed for repeated use
(3) other means acceptable to authority having jurisdiction
To prevent any damage to private property caused by thermal expansion, you are responsible to have a licensed plumber inspect your plumbing system to determine if there is a closed plumbing system. If so, you should have the plumber install an appropriate device to eliminate the problems that can occur because of thermal expansion. Failure to address this potential problem within your premises may cause damage to your water heater and/or plumbing system.
|
