RV Water Heaters: What You Need to Know

RV Water Heaters

An RV water heater will help you enjoy hot water wherever your travels take you. They operate much like a residential water heater, and yet very differently. Here’s a few things you need to know if you own an RV or you’re in the market. Knowing how these water heaters operate, how to maintain them, and what to look for if they are not functioning properly, is the key to keeping them running smoothly.

About RV Water Heaters

RV water heaters are much smaller than residential heaters, with a storage tank capacity of 6 to 10 gallons. However, there are “16 gallon heaters” available. But in reality, these units only have a 10 gallon tank and heat the water to a high temperature. The hot water is then mixed with cold at the faucet. By mixing the water, the unit can typically deliver 16 gallons of hot water.

Although, a bit more expensive, tankless water heaters are gaining popularity on RV’s. They function the same as a residential tankless heater, and are able to provide hot water in a matter of seconds on-demand.

Besides enjoying an “endless” supply of hot water, one of the many positive points of going tankless is the reduced demand of fossil fuel. A traditional RV heater will keep the water in the tank hot, which means that it is constantly cycling on and off . . . regardless if you are using hot water. A tankless heater will only use propane when you need hot water, which results in less propane used, and fewer tank refill trips.

Fuel Source Options

There are 3 primary fuel source options for RV water heaters.

  1. Electricity and Liquid Propane (LP) – The majority of RV water heaters are designed to operate on both electricity or Liquid Propane. This flexibility allows for the use of the most convenient power source, as well as the ability to utilize both fuel sources to bring the water to temperature quickly.
  2. Liquid Propane (LP) – Some RV’s, particularly the entry level models, are designed to operate with water heaters that only burn Liquid Propane.
  3. Motoraid – RV’s outfitted to heat their water in this manner utilize a more sophisticated fuel source. The Motoraid heating method utilizes the RV’s engine cooling system to heat the water. When the engine is running, water from the engine’s cooling system is circulated through embedded tubes in the water heater. As the water circulates thru these tubes, the water in the tank is heated.

Understanding Your RV Water Heater 

Electric Mode

If you have 120v of shore electricity or generator power, you have the ability to run your water heater in electric mode. However, it does require about 12 amps of electricity, which is a fairly substantial draw, so you may choose to use LP Gas Mode if power is limited.

Being aware of your RV’s shore power wiring (some only have 30A) and the outlet power available for the RV to plug into (30A or less) is also a consideration. If this is the situation you are in, you can always switch to LP Gas Mode, or simply turn off the water heater temporarily.

Liquid Propane (LP) Mode

There are several different model types of liquid propane (LP) water heaters. The primary difference is the ignition system. Higher end RV’s tend to have the Direct Spark Ignition, which is a more sophisticated system.

Manual Pilot Light

This is the most basic model, and utilizes a pilot light that needs to be manually lit.

If the pilot light is off, either by switching the Pilot Control switch to Off or it goes out unnoticed, gas is not allowed to flow. This safety design prevents danger from the LP gas leaking.

The pilot light should not be lit when the RV is traveling. The wind will blow the pilot light out. Although, this may be a minor inconvenience, it only takes about 20 minutes to have hot water.

Direct Spark Ignition

The Direct Spark Ignition (DSI) is the most common RV water heater. Since there is not a pilot light, the gas mode thermostat sends a signal to the heater control circuit board which opens the gas valve. The igniter is activated and, if all goes as it should, a flame develops.

A sensor detects the flame, and if no flame is detected after about 15 seconds, the gas valve is closed and the system shuts down. An indicator light will signal that the heater failed to light and the water heater will need to be turned off and on to reset the unit before another attempt can be made.

Although DSI Heaters can operate while the RV is traveling,  many owners prefer to wait until they arrive at their destination so they do not waste fuel.

RV Water Heater Maintenance

During normal use, RV water heaters require very little care. The Electric mode of the heater is maintenance free for the most part. Maintaining your RV heater is pretty straight forward and something you should be able to do yourself if you choose.

Anode Rod

The anode rod is designed to sacrifice itself and prevent the steel tank from corroding. Many RV owners recommend changing the Anode Rod every year if the tank is made from steel. Some tanks are lined with glass, and don’t use anode rods.

In order to remove the anode rod, you’ll need a socket wrench. If it has been awhile since it has been pulled there may be rust and corrosion making it difficult to remove. Expect to get wet, as the water and sediment debris will pour out once you pull the rod.

Tank Flush

RV water heaters should be drained whenever the RV isn’t in use. For proper instructions on how to drain a water heater, click here.

For a few dollars you can purchase a water heater tank rinser. These wands are designed to spray water into the back of an empty tank. You’ll be able to easily flush the inside of your tank and remove the sediment, which is critical in extending the life of your water heater.

Winterizing the Water Lines

The hot water heater is large enough that it should be able to expand and contract without damage, provided it has been properly drained. However, the water lines are typically very thin and need to be filled with anti-freeze.

Many water heaters are equipped with a bypass valve to keep anti-freeze in the water lines and out of the tank. If you’re water heater doesn’t have a bypass valve, kits can be installed that perform the same function.

If you do fill your heater tank with anti-freeze, be sure to thoroughly flush the tank before refilling it for use.

Burner Tube Cleaning

The burner tube should be cleaned annually in the LP Gas mode to keep it free of debris. This can be done by simply using a vacuum cleaner nozzle or spraying compressed air. It’s best to do this in the Spring.

RV Water Heater Troubleshooting

Gas Supply Tube

The most common reason a RV Water Heater won’t operate is because the gas supply tube becomes plugged. When there are obstructions in the gas supply tube, gas isn’t able to make it’s way to the pilot assembly.

Small insects and spiders are drawn to the smell of propane, and they commonly build nests inside the tube. This can be easily prevented by cleaning the tube when you first pull your RV from storage, and periodically throughout the season.

ByPass Valves

You’ll need to do a little trouble shooting to solve this common problem. First check the pressure relief valve outside to determine that the water is hot. Once you’ve established that the hot water isn’t making it’s way to the faucet, there’s a good chance the solution is as simple as checking your bypass valves to ensure they are all correctly positioned.

  • If there is no hot water after the heater has cycled on and off, check the hot water valve. If it is still in the off position, no water will be allowed to flow.
  • If the hot water flow turns cold quickly, the bypass hose is likely still open and the heated water is mixing with cold water.

Electric Heating Elements

This is also a very common problem and frequently happens in the Spring. People tend to forget to take their water heater out of winterization bypass.

It is critical to make sure that there is water inside the tank before using the electric mode for the water heater. Without the water in the tank to draw the heat away from the heating element, the heating element will burn out.

Fortunately, replacing a heating element is a relatively easy and inexpensive repair.

Unpleasant Smell

An unpleasant smell coming from the faucets is likely the result of stale water. This can happen to both the cold and hot water, but tends to be worse with the hot water.  Simply drain the tank and the water in the lines. When you refill your tank, the smell should be gone.

How Long Will an RV Water Heater Last?

The life span of an RV water heater depends on a number of factors, but with proper care, they can still be operational up to 10 years. Draining and flushing your tank, changing the anode rod, and other annual tasks will help keep your water heater working for years.