Let’s talk about RV Water Heaters
Most RVs come equipped with a water heater. There are some exceptions, like pop-ups and other small RVs. RV water heaters come in different sizes, different modes of operation, and are made by different manufacturers. The tank size and the method used to heat the water will dictate the amount of hot water you have available, and the amount of time it takes to heat or re-heat the water. The majority of RV water heaters have a 6-gallon water tank, but some larger and more expensive RVs have 10-gallon or 12-gallon water heater tanks. To keep pace with technology, tankless or demand type water heaters are more prominent in today’s RV marketplace.
RV 101 Tip: Atwood and Suburban are two common brands of water heaters used in RVs. Atwood water heaters use an aluminum clad tank which is lightweight and corrosion resistant. Suburban water heaters use porcelain lined steel water heater tanks, and incorporate an anode rod designed to prevent the steel tank from corroding. We’ll talk more about the anode rod in a minute.
Modes of Operation
RV water heaters operate on LP gas, and some models offer a combination LP gas/ 120-volt AC option. There are three basic types of water heaters used on RVs.
- There are manual water heaters that you physically light
- There are electronic ignition, or Direct Spark Ignition (DSI) water heaters that you light by turning on a switch
- There are LP gas tankless or demand type water heaters that provide instant hot water when you open a hot water faucet
Using the RV Water Heater
Caution: Never light the water heater unless you are sure the water heater tank is full of water. Make sure the water heater is not bypassed. You know the water heater tank is full when you turn a hot water faucet on and get a steady flow of water. If it is spitting air or air and water the tank is not completely full.
RV 101 Tip: When you connect the RV to a city water source, or draw water from the fresh water tank, via the water pump, the water heater will fill with water automatically unless it is in the bypass mode.
Caution: Keep children away from the exterior water heater vent. It can get extremely hot. All of the LP gas appliances on the RV are vented outside with the exception of the range burners and the oven.
Most RV water heaters have bypass kits installed. The water heater bypass is typically used to winterize the RV. When no water supply is coming into the RV, you drain the water heater tank, and then set the valves to bypass the water heater. Bypassing the water heater accomplishes two things:
- When you winterize the RV, you don’t need six or more gallons of RV antifreeze just to fill the water heater tank.
- It prevents any water left in the tank from freezing, expanding, and rupturing the tank.
You don’t see as many (manual light) water heaters as you used to. A manual light water heater has a manual gas valve.
If you look at the dial you see an Off, On and Pilot position. To light the water heater, move the selector to the pilot position. The dial is spring loaded. Hold it down in the pilot position and use a striker to light the pilot light. Continue holding it in this position for several seconds after the pilot is lit. When you release the knob and the pilot light stays lit, turn the knob to the ON position and the burner will light. You want to see a nice strong, blue flame.
It takes approximately 20 to 30 minutes to heat the water to temperature. The water heater will cycle on and off as required. You have the option to leave the water heater on for your entire camping trip, or just light it 30 minutes before you want hot water.
If you have a DSI, or Direct Spark Ignition water heater, make sure the water tank is full, turn the switch on and it will light automatically. If it doesn’t light the red indicator will illuminate and you need to turn the switch off and then back on. If the water heater still does not light:
- Check to make sure the LP gas supply is turned on, and that you have LP gas in the cylinders or tank.
- Make sure you have 12-volts going to the water heater’s circuit board by way of a 12-volt auxiliary battery on the RV, or through the RV’s converter if you are plugged into electricity.
Some RV water heaters offer an additional feature where it operates on 120-volt AC electricity. If you are plugged into a 120-volt electrical source turn the water heater switch on in the electric mode. Keep in mind it will draw 9 to 13 of the available amps you have when it’s in the electric mode, and always make sure there is water in the tank so you don’t damage the electric heating element. It will take a while longer to heat the water in the electric mode.
I mentioned earlier there is a third type of water heater called a tankless or demand water heater. On demand water heaters use LP gas as the source to heat the water. You just flip a switch to turn the water heater on and whenever you open a hot water faucet in the RV the water is heated on-demand. You not only get instant hot water, you get a continuous supply of hot water, whereas other types of water heaters use the heated water in the tank and require additional time to recover and re-heat the water.
RV Water Heater Maintenance
There are a few RV preventive maintenance (PM) checks and procedures we as RV owners can perform to help keep the RV water heater in proper operating condition.
I recommend draining the water heater tank after each trip, unless you have another trip planned in the near future. Draining the tank will help prevent stale water and odors. To drain the water heater, turn the water supply coming into the RV off. Relieve the pressure by opening a hot water faucet in the RV. Remove the drain plug, located on the left bottom or center bottom of the water heater. You can open the Pressure Relief Valve at the top of the water heater to assist in draining the tank.
Caution: Never drain the water heater when it is hot, or under pressure.
RV 101 Tip: Atwood water heaters use a nylon drain plug. It is easy to round the drain plug corners off as you remove the plug. I recommend keeping a new drain plug on hand in the event this happens when you are traveling. Suburban RV water heaters use an anode rod with a 1 1/16” end.
If you have a Suburban water heater, it will have an anode rod. The anode rod protects the steel lining in the tank by self-sacrificing the rod rather than the tank itself. To drain a Suburban tank, you remove the anode rod. Every time you drain the tank inspect the condition of the anode rod. When it is 75% depleted you should replace it with a new rod.
Caution: Never drain the water heater tank when the water is hot or under pressure. This could result in severe burns. To relieve the water pressure turn the water supply off and open a hot water faucet. Allow sufficient time for the water in the tank to cool prior to draining the tank.
Draining the water heater tank is helpful, but it won’t get rid of the mineral deposits and debris that collect in the bottom of the tank. This is primarily because the drain plug is located higher than the bottom of the tank. To extend the life of the water heater tank and remove the mineral deposit build-up you need to flush the water heater tank periodically. I recommend flushing the tank twice a year at a minimum.
You can purchase a flushing tool designed specifically for this job. Connect the flushing tool to a water hose used for maintenance, and turn the water on. Place the tool in the water tank drain and open the valve on the tool to flush the sediment from the sides and bottom of the tank. Continue to flush the tank for several minutes. When the water coming out is clean and clear you can stop flushing.
Maintaining your RV water heater will add years of life to the water heater.
This was a good primer on using and maintaining RV water heaters. To learn more about this, and many other RV topics visit RV online training
Mark J. Polk
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