Ask the RV Doctor – Just Add Hot Water

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February 12, 2013

by Gary Bunzer

Q: I purchased a truck camper recently which does not have a hot water system which I am planning on installing. Could you provide me with a basic RV water system schematic? I have a good idea of the basic layout of water lines and components but I’m not sure where the check valves should be placed to prevent unwanted backflow. Any help would be appreciated.
—Albert Lepore, Rochester, NY

A: Albert, I don’t have a diagram for you, but it is easily understood logic. At the back of the water heater, you’ll find a cold water inlet and a hot water outlet. Obviously, you’ll connect the existing cold water line to the cold inlet. This is the point where you’ll also want to install a one-way check valve directly to the cold water inlet with the directional arrow pointing into the tank. This will prevent heated water from migrating out of the water heater and feeding back into the cold system. This usually isn’t an issue unless the cold water line tees off to another fixture very close to the back of the water heater. I have seen where the cold connection to the toilet was tee’d very close to the inlet of the water heater and every time the owner flushed the toilet, steam would rise out of the toilet bowl. Installing a check valve at the water heater inlet curtailed that immediately. Most RV manufacturers now do this at the factory. From the hot water outlet on the water heater, simply route the water line to every faucet with a hot water valve. Typically you’ll end up with three fresh water check valves: one at the cold inlet to the water heater, one at the city water inlet and one located at the outlet of the water pump. When on city water, you’ll want to keep water from entering the pump and when operating the water pump, you want to keep the water from spewing out the city water inlet.

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