RV Water Heating Systems
The hot water system doubles the plumbing in an RV. Beyond the pump and the city water valve, are the hot water tank and a complete separate plumbing system to each sink and shower installation.
The water heater consists of an insulated storage tank of six to ten gallon capacity, and a propane gas burner that is used to heat the water. The storage tank is made of aluminum or glass-lined steel, depending on the model. The steel tanks use an anode rod to help prevent corrosion of the tank material. The corrosive elements in the water attack and "eat up"the anode rod rather than the material of the tank. These anode rods should be inspected and replaced annually, if required. Aluminum tanks do not require an anode rod.
Additional options include electrical heating elements and motor assisted hot water systems in some motor homes.
The cold water in the water heater expands as it is heated thus increasing the water pressure. This additional pressure may cause the temperature/pressure relief valve to "weep" and cause other leak problems. The RV water system is designed for water pressures of about 45 PSI. If the city water connection is hooked up to a water source, a water pressure regulator should be used to control the higher pressure. This pressure, along with the added pressure from the heated water may cause leaks to develop.
The water heater is designed to trap a pocket of air above the water level in the tank. This air pocket compresses as the water is heated. The air pocket can eventually be absorbed by the motion of the vehicle and should be restored from time to time.
To restore the air pocket, turn off the water pump or city water supply and open a hot water tap to reduce the water pressure to zero. Remove or open the water heater drain plug or valve. Allow the water heater to drain and flush it by running water through it for several minuets. Insert the plug or close the drain valve and re-fill the water heater tank until the water appears at the opened hot water faucet.
Another solution would be to add an accumulator to the system. An accumulator tank is basically a sealed tank in the water system that has an air pocket to absorb extra pressure.
See also: RV Water Heater Servicing.