Why Is My RV Hot Water Heater Not Working?

Hot water access is one of the biggest advantages that RVers enjoy. But when an RV hot water heater is not working, it’s more frustrating than going on a tent camping trip knowing you’ll have to use the campground facilities for dishes or a warm shower. 

If you’re not getting hot water in the camper,  start troubleshooting with these basic questions:

Is the Water Heater Turned On?

Turn on the switch for your gas/electric or tankless water heater. For gas/electric water heaters, you must turn on the switch for several minutes to heat water in the tank before using hot water at a faucet or showerhead. Even after the water heater is turned on for several minutes, you may need to open the hot water faucet for 10 or 15 seconds to purge any cold water resting in the lines.

How Long Has It Been Turned On?

Unless you have an on-demand or tankless water heater, the gas or electric heating option takes time to warm the water in the tank. The larger your water heater’s tank (usually 6 or 10 gallons, but 12 and 16-gallon models also exist), the more time it takes to heat the volume of water stored inside. 

With gas/electric water heaters, it typically takes between 30-45 minutes for the water in the tank to heat. However, you can use both heating settings for “quicker recovery,” which reduces the amount of time you’ll need to wait before hot water is available.

With tankless water heaters, hot water should be available at your faucets and shower within 5-10 seconds of turning the heater’s switch to the On position.

Have You Run Out of Hot Water?

The average RV water heater tank holds about 6 gallons, while residential tanks average about 40 gallons. If your family takes multiple showers back-to-back, you’ll need to space them out enough for your water heater tank to refill and reheat. The average tank-style water heater can provide hot water for 5-10 minutes, depending on tank size.

With tankless water heaters, there are fewer limitations because there’s no tank to fill and heat. However, the “unlimited hot water” that many tankless water heater manufacturers boast can be misleading because you are limited by other factors in your RV’s plumbing system – mainly gray water tank capacity, but also fresh water tank capacity when dry camping. 

Technician Tip: On-demand or hybrid systems such as the Aldi or Truma Combi may not match the temperatures of tank-style and tankless water heaters. The problem is that they may use the same or similar names, such as tankless or on-demand, which can be misleading. All types will list the GPH, gallons of water at the advertised temperature, and the setpoint temperature of the system. The RV owner must look for and compare these real-world data points in order to get what they require for their personal needs.

Is Air in the Propane Lines?

If the gas switch is turned on and the unit is trying to heat water, you should hear the roar of the flame (without opening the water heater access door). If the flame is not lit, ensure the valves on top of your propane containers are fully opened. Then, light a burner on the stove to test that gas flows through the camper.

If you recently refilled your ASME tank or changed out for a new DOT cylinder, there may be air in the LP lines, causing the water heater to misfire. Lighting the burner on the stove should purge most of the air and ensure a steady LP supply to light your water heater.

Is There Sufficient Voltage to Keep the Gas Valve Open and Circuit Board Active?

It takes a minimum of 10.5 volts to hold open the coils on the gas valve. Low voltage is more common when dry camping because you aren’t connected to a reliable campground power source. If your battery is drained, your water heater won’t have enough power to operate as intended. If you suspect this could be the case, use a digital multimeter to test the DC voltage on your RV battery (or batteries).

Is Water in the Tank?

To check for an empty tank, start by turning off the gas and/or electric control switches. Go outside and open the heater’s access cover. Gently touch the pressure-temperature valve (P/T valve) and see if it is hot. If it is, the appliance is trying to create hot water. However, there may not be water in the tank.

Grab a coffee cup and place it under the P/T valve opening. Lightly pull up on the silver lever at the head of the valve. Hot water should run into the cup. If you hear a quick air pressure release and no water comes out, there is no water in the tank. 

At this point, it’s time to stop. The most likely scenario is that your water heater’s bypass valve is still in winterize mode. Resetting the bypass valve once the water heater has been running will add cold water to a hot tank, which can cause irreparable tank damage.

The cold water will crack the glass lining in a Suburban tank. On a Dometic tank, it will likely collapse or crack the flue tube that runs through the center. The cold water will also crack an electric heating element.

On pilot models, running the water heater for a short time without a full water tank will cause the high limit switch in the thermostat assembly to open permanently. The result? You must replace the entire assembly, as it is neither resettable nor serviceable.

Wait 60-120 minutes for the tank to cool before changing the bypass valve to the normal operation position and adding water.

Is Hot Water Coming From the Cold Faucet?

If you’re trying to get hot water at a single-lever faucet, the mixing valve on the faucet might be faulty. Try getting hot water from the cold side. During the camper’s maiden voyage, we sometimes discover that the hot and cold lines were installed incorrectly by the manufacturer. If you suspect this to be the case in your RV, contact a service center for further assistance to remedy the issue of your RV hot water heater not working.

Is the Water Heater Warm, Not Hot?

If you feel that your water isn’t getting hot enough, there’s a quick and simple test. Get an inexpensive meat thermometer and fill a coffee cup with hot water. If the cup is cold, dump and refill it several times to bring it to temperature. Drop the thermometer into the water. 

Tank-style water heaters typically heat to 140℉. A thermometer reading of roughly 140℉ is normal if you fill the cup at the P/T valve. A thermometer reading around 120℉ is more likely when drawing water from a faucet. If the water heater utilizes a mixing valve, such as the EXT models, the water at the P/T valve may reach 180℉, which can be dangerous even though it is ultimately tempered down to the same 120℉ at the faucet.

Contact a Camping World Service center to schedule a more complete diagnostic if your test reveals that your hot water heater isn’t heating to the designed temperature.

Technician Tip: Consult your owner’s manual or manufacturer for information on your water heater’s intended temperature if you don’t have a Suburban or Dometic model.

If you’ve asked these questions and tried the troubleshooting tips associated with each, but you’re still not getting hot water, it’s time to schedule an appointment to have your water heater inspected by an RV technician. 

For other troubleshooting tips, check out these articles: 

• What’s an Anode Rod for RV Water Heater?
• How to drain an RV water heater
• What Is a Digital Multimeter? (And Why RVers Need One)
• Why Does My Freezer Keep Frosting Up?
• Why Is My RV Water Pump Not Working?

Do you have additional questions about why your RV hot water heater is not working? Let us know in the comments below.