Thermal Actuating Valves (bypass valves/comfort valves) open and close based on the temperature of the water contacting the valve. Engineers have identified these valves as the main cause of a homes loss of cold water comfort. These valves open / close based on the temperature of the water which contacts them and rely on the systems heater mounted pumps pressure to overcome the opposing pressure of the cold water line at the bypass valve. The problem is that anytime cold water within the home is used, the pressure in the cold water line drops allowing water from the hot water side to easily pass through the comfort valve / bypass valve and into the cold water line. During this inefficient bleedover, cold city water enters the home hot water heater to replace the water which bled through the bypass valve. This inefficient bleedover continues until water hot enough to close the comfort valve reaches the comfort valve. This is a significant waste of valuable thermal energy and is the cause of homeowners loss of cold water comfort in their home. Depending on how often the cold water is used, this inefficiency has the potential of seriously raising the homeowners water heating bill. Recirculation systems which have their pumping mechanism attached at the water heater and have crossover / bypass / comfort valves connected at the most distant fixture from the water heater utilize these inefficient temperature actuation type valves.
1st Inefficiency inherent with these valves is they cannot maintain positive closure when +45 pounds of opposing water pressure is forced on them, as when a faucet or tap is open. Thus, leaching between hot and cold water lines occur every time the water lines pressure drops, i.e. laundry, dishwasher, icebox refill, toilet flush, sprinkler system, etc.2nd Inefficiency inherent with this type of recirculation system is that during scheduled-on periods the pump runs continuously consuming valuable electrical energy even when hot water has filled the hot water pipes. This also causes undo wear on the pump shortening it's lifespan.
Homeowners unknowingly have these type systems installed in their home because they just don't have an electrical outlet under their fixture / sink that's farthest from the homes water heater, believing they'll be saving money by not paying to have an outlet installed. But, in the long run, they'll actually be wasting serious energy and the comfort of cold water every month. These major flaws result in homeowners complaining of loss of their homes cold water comfort making them waste water down the drain in order to get cold water from their homes cold water line when they should be addressing the wasted thermal energy that their paying for each month.