The Expansion Control Valve (ECV) is designed to relieve the increase in pressure caused by the water expansion during the normal heating cycle. It is recommened that an ECV be fitted to the cold water supply line. This will relieve cold water, not hot water, during the heating cycle saving energy and increasing the life of the Pressure Temperature Relief valve (PTR). Some local governments make it mandatory to install an ECV in the cold water line. PTR and ECV valves are safety valves and should be replaced every 4 years.
