Is crossover hot water recirculation a good choice for branch-type piping configuration?
I am considering replacing my aging hot water heater with a tankless. Several products offer a recirculation feature that sounds appealing, but I am uncertain whether recirculation would work for the unique way that piping has been run through my house.
The diagrams that manufacturers use to describe crossover hot water recirculation show a pair of long main lines that serve each of the fixtures from pairs of short branches. A thermal bypass valve is installed in the fixture that is farthest from the hot water heater, and the recirculation occurs through that valve. My understanding is that recirculation occurs only through the loop between the hot water heater and the thermal bypass valve; and that there is no recirculation to the fixtures that do not have a thermal bypass valve (but who cares? they are so close to the main that is carrying the recirculated water that it won’t take long for hot to get there).
My house is 110 years-old, and has undergone several different remuddles that each added new fixtures to an existing system. My hot and cold water mains (if you can call them mains) are only 18” long, with 10’, 20’ and 40’ branches that serve single fixtures or small groups of fixtures.
My assumption is that if I opt for a hot water heater with crossover recirculation and install a thermal bypass valve in one of the second-floor bathrooms, then only the second floor bathrooms will get the recirculation; and the fixtures on the other branches will have to wait for hot water.
My three questions are:
- Is my assumption correct; will recirculation occur only on the loop/branch that has the thermal bypass valve?
- Can I get whole-house recirculation if I put a thermal bypass valve
at the end of each branch?
- Is crossover hot water recirculation a good choice for branch-type