An apparatus connectable between a hot water supply and a plumbing fixture hot water outlet and a cold water supply and a plumbing fixture cold water outlet, wherein the hot water outlet and the cold water outlet flow through a flow restrictor, the apparatus adapted for diverting into storage the initially cool portion of a hot water stream from the hot water supply and to discharge the diverted cool portion from storage upon opening of the plumbing fixture cold water outlet, comprising:
- an accumulator having a pressure biasing member therein;
- a hot water flow control valve having a thermostatic actuator selectively connecting the hot water supply to a cool water outlet when the temperature of water flowing through said hot water control valve is below a predetermined temperature or to a hot water outlet when the temperature of the water flowing through said hot water control valve exceeds the predetermined temperature;
- said cool water outlet flow connected to a cool water inlet of a hot water request valve;
- said hot water outlet flow connected to a hot water outlet line which is flow connected to the plumbing fixture hot water outlet;
- said hot water request valve having a first piston selectively connecting said cool water inlet to a cool water discharge port in said hot water request valve when said plumbing fixture hot water outlet is opened and blocking said cool water discharge port from said cool water inlet when said plumbing fixture hot water outlet is closed;
- said cool water discharge port of said hot water request valve flow connected to a cool water trunk line which splits into a storage branch flow connected to said accumulator and a cool water discharge branch flow connected to the plumbing fixture cold water outlet;
- a cold water flow control valve having a cold water inlet flow connected to the cold water supply, a cold water outlet flow connected to the plumbing fixture cold water outlet and a second piston;
- said second piston selectively advanceable between a closed position in which said second piston blocks said cold water outlet from said cold water inlet and an open position in which said second piston is withdrawn from blocking said cold water outlet from said cold water inlet thereby flow connecting the cold water supply to the plumbing fixture cold water outlet;
- said second piston is in communication with said cool water discharge branch and said cold water supply and configured such that pressure in said cool water discharge branch advances said second piston to said closed position until the pressure in the cold water supply exceeds a preselected multiple of the pressure in said cool water discharge branch;
- said pressure biasing member increasing the pressure exerted on water in said accumulator, said storage branch and said cool water discharge branch as the volume of water in said accumulator increases;
- wherein
- water flowing into said cool water trunk line through said hot water request valve flows into said accumulator through said storage branch until the pressure exerted on the water in said accumulator by the pressure biasing member approaches the pressure of the water flowing into said cool water trunk line;
- and when said plumbing fixture cold water outlet is opened, water contained in said accumulator is urged out of said accumulator and out said plumbing fixture cold water outlet through said storage branch and said cool water discharge branch until the pressure of the water in the cold water supply exceeds the preselected multiple of the pressure in the cool water discharge branch exerted thereon by said pressure biasing member in said accumulator;
- wherein the apparatus further comprises:
- pressure compensating means flow connected to said hot water outlet line upstream of said hot water outlet and to said cold water stream between said accumulator and said cold water outlet for restricting the flow through the hot water outlet line when the pressure in the cold water stream decreases to thereby concurrently increase the flow from said accumulator through said cold water outlet.