US Patent 8245946 Method and apparatus for conserving water

A unitary valve block assembly is interposed between a hot and cold water outlet and a faucet assembly including a hot and cold valve to convey the initially cold portion from the hot water outlet into an accumulator during all the times when the accumulator is substantially unfilled. This accumulated water is then emitted through the cold water valve each time cold water is demanded. When the pressure ratio between the accumulator and the water source indicates that it contains substantial quantities of un-evacuated stored water the subsequent demands of hot water are conveyed directly to the hot water valve regardless of the temperature thereof.