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 is basically a sealed tank in the water system that has an air pocket to absorb extra pressure.

An anode rod is used to help prevent corrosion of a steel water heater tank. The corrosive elements in the water attack the anode rod instead of the steel tank. The anode rod should be inspected yearly and replaced as needed.

Aluminum tanks have a special inner coating and do not use an anode rod.

Atwood tanks are lined with a material that acts as an anode rod, so therefore no anode is needed. Suburban uses a glass-lined steel tank and a sacrificial anode rod (magnesium) is used to prevent the steel from being attacked.

I don't see more Atwoods with corroded tanks as compared to Suburban tanks. (in my neck of the woods). I have seen anode rods in Atwood tanks that were impossible to remove, and a welder friend explained that it is the different metals that causes this. The anode rod threads are steel and the tank threads are aluminum. This is why Atwood uses a nylon plug for the drain and does not recommend replacing it with a brass or steel one. I suppose if the anode rod was installed with teflon tape or a plumbers pipe sealant this problem would be eliminated, but would the customer remember to do this every time the anode is removed and replaced?

I hesitate to recommend anything to a customer that the manufacturer advises against. If something goes wrong the customer comes back, even years later, and says "You recommended such and such, now you owe me a new thingy"! Also, I figure that the manufacturer is the best one to recommend something to do with their product.

I do recommend flushing the hot water tank occasionally to get rid of the sediment and corrosive deposits in the bottom of the tank. Just pull the drain plug, allow it to drain, and direct a stream of water into the drain hole to agitate the sediment. Then allow it to drain, repeat until the water comes out clean. Do this about every other month (or more if your water has a lot of minerals) The flushing also helps to eliminate any hydrogen sulfide that may build up in the tank (causes the rotten egg smell in the water), and makes the heater more efficient.