What is a Balance Reducing Valve

Inspecting a new home yesterday I saw a copper line from the cold water supply to a drain line. The water was on and there was no discharge from the drain pipe. The builder responded with this explanation. "
That is a BRV (Balance Reducing Valve). You have a PRV (pressure reducing valve) that is tied into the main water line in the flower bed. If that was to fail, the BRV valve will keep the water heater in check and keep it from leaking."

Can anyone enlighten me on this?




Series: **BRV **
Description: Combination Ball Valve and Relief Valves
Size Range: 3/4 to 1 in. (20 to 25mm)

Series BRV Combination Ball Valve and Relief Valves are used in commercial and residential applications on water heater installations. It consists of a bronze body construction with a full port (reduced port with PEX connection), nickel-plated brass ball, blowout-proof brass stem, PTFE seats, stem packing, and stem thrust bearing, Viton relief ball, stainless steel relief spring, brass adapter, and steel handle (the relief valve outlet includes a drain tube connection with PEX or compression fitting models). Series BRV has a low profile design and can be installed in any position. It is for applications that require a means to shut off the water supply to the water heater and for providing protection from excess water pressure caused by thermal expansion. Pressure Rated: 400psi. Relief Valve Pressure Settings: 75, 80, 100 or 125psi (5.2, 5.5, 6.9 or 8.6 bar).

Thank you.

Does this take the place of an expansion tank?


Yes, if permitted in your jurisdiction.

I appreciate the help.