Closed Water Systems

Water supply systems may, because of code requirements or such conditions as high line pressure, among others, have installed devices such as pressure reducing valves, check valves, and back flow preventers. Devices such as these cause the water system to be a closed system.

THERMAL EXPANSION

As water is heated, it expands (thermal expansion). In a closed

system the volume of water will grow when it is heated. As the volume of water grows there will be a corresponding increase in

water pressure due to thermal expansion. Thermal expansion

can cause premature tank failure (leakage). This type of failure

is not covered under the limited warranty. Thermal expansion can also cause intermittent pressure relief valve operation: water discharged from the valve due to excessive pressure build up. This condition is not covered under the limited warranty. The pressure relief valve is not intended for the constant relief of thermal expansion.

A properly sized thermal expansion tank should be installed on all closed systems to control the harmful effects of thermal expansion. Contact a local plumbing service agency to have a thermal expansion tank installed.