Water heaters used in today’s RV have come a long way since the old manual start models. There are also several types such as 6 gallon liquid propane (LP) fueled, 6 and 10 gallon LP and 120-Volt electric powered, and even on demand systems. All these systems operate very similar to residential models and need little maintenance, however there are some things you need to understand to make them run more efficient and keep them running.
One of the most important aspects of a water heater is making sure you drain the water during storage and winterize it with either RV antifreeze or make sure there is no water in the tank and lines. If water is in the tank and it freezes, it will split the inner tank and ruin it. Typically there are two main water heater manufacturers, Suburban and Atwood. Both have a drain plug that will allow you to drain the water.
This picture shows a typical Suburban water heater with a metal drain plug with an anode rod. The anode rode acts as a sacrificial metal to prevent the tank from rusting. The Suburban tank is aluminum and does not need the rod. When draining the tank it a good idea to inspect the anode rod if your unit has one and replace it if it’s badly corroded.
Once the water is drained you will need to either fill the entire tank with RV Antifreeze or another method is to bypass the water heater and leave it empty.
This valve diverts the water away from the system and allows you to fill all the remaining lines with RV antifreeze and not waste 6-10 gallons filling the tank. If your system does not have a bypass valve, there are aftermarket kits that are easy to install. The other option is to make sure all the water is removed not only from the tank, but also all the lines in the system.
If you are storing your rig in an area that is not cold it is still a good idea to drain the tank just in case and also to get rid of standing water that can eventually not only get very stale and smell bad, but can also create mold and mildew.
When you are ready to bring the unit back out of storage, make sure there is water in the tank before starting it up! Running an electric water heater without a full tank will burn out the electric heating element.
Periodic Tank Maintenance
Since you will be using hard water from campground source a fair amount of the time, sediment such as calcium, rust, lime, and even sand can accumulate in the tank. Therefore it’s a good idea to drain the tank and flush it periodically with fresh water and a garden hose.
If you detect a Sulphur or other bad smell, run the cold water first to determine if it’s coming from the fresh water tank. Then run the hot and to isolate if it’s hot or cold. To sanitize the hot water tank you can use chlorine bleach mixed to the recommendations on the side of the bottle, vinegar and water, or one of the various fresh water sanitizers available on the market.
It is also a good idea to periodically clean the burner assembly and air shutter tube. Use an air compressor with a blow gun and make sure you wear safety glasses.
Pilot Light Models
Inexpensive water heaters still require a manual lighting of a pilot light. Refer to the original equipment (OEM) owner’s manual for this procedure. Typically the procedure starts with making sure the propane tank valve is on and you have propane. Turn the control knob to pilot. This position is spring loaded so hold the control knob down and light with a long match or butane lighter with long extension and hold the knob down for approximately one minute or until it will stay lite.
Once the pilot stays on permanently, move the knob to the On position. Some models also have a temperature knob that will allow you to set the desired temperature.
Direct Ignition Start (DSI) Models
The DSI models are easy to start, simply verify the LP is on at the tank and push the On switch usually located at the monitor panel. This activates the module board which is connected to the thermostat at the tank. As the water temperature falls below the preset temperature, the module board opens the gas valve, starts the spark ignitor similar to what the pilot light would do, and starts the heater. Once the water in the tank gets to the preset temperature it will shut off.
This photo shows the thermostat as well as the emergency cut off (ECO) switch in case the unit gets too hot.
If you notice water dripping or “weeping” out of the pressure relief valve located in the above photo with the yellow label, this is normal. The tank should not reach over 210 degrees or 150 psi and if the system is running for a long period of time, it will typically reach 150 psi and simply “weep” out the additional pressure. If it continues, the valve has either corroded or has become weak and defective.
In the case of a pilot light model water heater not functioning, first verify there is LP in the tank and the valve is on. This can be determined by lighting another LP appliance such as the stove top. Next, verify 12-volt power is coming to the module with a multimeter. If the pilot light is working, and the water temperature is not hot, there typically is a temperature lever that you can adjust. Check your owner’s manual for location and settings. If the flame is not a consistent blue, check the air shutter to make sure it’s at the recommended opening. Typically it should be 1/4 open, again check your owners manual.
The factory thermostat is typically 110-14- degrees, if the water temperature is not getting hot check your air shutter setting, burner assembly for blockage, improper burner adjustment, or blocked u-tube.For Direct Spark Ignition (DSI) Models, the thermostat is factory set at 140 degrees and is not adjustable. The unit will start when the water temperature drops below 115 degrees and shuts off at 140 degrees. This typically takes 20-25 minutes. Some models do have an optional thermostat that can be adjusted from 110-150 degrees. If the unit will not start check the following:
- Gas present but no spark – check the wires connected to the circuit/module board to ensure they are tight, check the electrodes at the spark assembly, check gap at electrode-should be 1/8”, and verify the porcelain is not cracked and sending the spark to a ground source. Otherwise the circuit board could be bad.
- Spark present but no gas – verify the power coming to the circuit board is at least 10.5 v DC, clean the burner tube and orifice, check for loose wires at the ECO and T/Stat, verify gas valves are on and correct gas pressure is at 11” of water column. A simple test for this is to start one burner on a stove top and verify a consistent blue flame, start a second and then a third. If the flames flicker and are low, your LP pressure regulator is probably bad.
- Insufficient or excessive water temperature – check to make sure the t/stat is properly seated to the tank, verify the burner assembly is working properly, if so, replace the t/stat.
If all above functions are working correctly, then it’s time to check the circuit or module board. This should be done by a certified technician.
Here is a simple test procedure from Atwood:
- Check all wire connections
- Check the integrity and position of the spark probe assembly
- Check the alignment of the main burner to the orifice
- Check the alignment of the flame spreader on the burner tube
- Check the air adjustment
- Check the cleanliness of the orifice
- Check for obstructions in the main burner tube
- Check the cleanliness of the flue tube
- Check the voltage to the valve
- Check the gas pressure of the RV
- Intermittent circuit board-if everything else checks out above, only then check the circuit board. Make sure it is clean, all connections secure and is moisture free before changing it out.
About the author: Dave Solberg: Managing Editor, RV Repair Club
For the last 25 years, Dave has conducted RV maintenance and safety seminars, developed dealer and owner training programs, written RV safety and handyman articles, authored an RV handbook reference guide and logged over 100,000 miles on the road in an RV.
RV Repair Club is your go-to online resource for enthusiasts who want quality RV maintenance, repair and upgrade information – a community where passionate RVers can come together to gather knowledge and share their experiences.
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Paul Goldberg said:
Although you mention “on demand” water heaters you provide no information about the care of them. Another article devoted to to them would be appreciated. I hae used two different On demand or tankless water heaters since 2012. They are very nice, but not trouble free.
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Hi, could you make a blog post where you’d explain a bit more in depth about these heaters? https://www.heatso.com/espar-airtronic-d2-heater-kit-12v-2kw/ I am really confused and idk how to set it up.
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