RV Hot Water Heater Not Working?

Hot water is one of the greatest conveniences for RVers. But when the RV water heater isn’t working? It can make your trip far less comfortable. In this guide, we’ll provide some DIY troubleshooting tips to help you identify and potentially fix your RV water heater issue.

Some of these tips include ways to resolve the problem once identified, while others may require the assistance of a certified RV technician. Let’s troubleshoot your RV water heater!

What Could Cause an RV Hot Water Heater Not to Come On?

There are two main reasons a propane RV water heater wouldn’t turn on as expected:

1. Lack of electrical power
2. Lack of liquid propane (LP) gas

Within those two broad causes, there are many possibilities you may need to track down. For example, here are some reasons why your RV’s hot water heater isn’t getting power: 

• Drained RV battery
• Blown fuses
• Tripped circuit breaker
• Faulty or damaged electrical wiring

Additionally, the water heater in your RV may not be lit because it’s not receiving LP gas as the result of: 

• Insufficient propane in onboard LP containers
• Damaged or leaking propane lines
• Air buildup in propane lines

What Causes an RV Water Heater to Stop Working?

How do RV water heaters work? Even if you’re still learning that answer, it’s not hard to tell when your water heater isn’t working. If your RV water heater was working but has stopped, the most common issue is running out of propane. It may also stop working if it’s no longer receiving DC power due to a blown fuse or tripped circuit breaker, which are relatively simple fixes that most RVers can check and resolve.

Another possible cause is the Energy Cut Off (ECO) switch being tripped. This safety feature automatically cuts power to the water heater if the temperature inside the heater tank exceeds a certain limit. The ECO switch combines a thermostat and high-limit control to prevent overheating. If this switch is tripped, contact an RV technician to diagnose and reset it. The underlying cause of the trip should be investigated to avoid further safety issues.

If your ECO switch is tripped, your safest path is to contact an RV service technician to complete a water heater diagnostic. Most water heater manufacturers outline resetting the ECO switch in their owner’s manual. However, the underlying cause of the trip should be investigated to prevent future safety issues.

RV Water Heater Troubleshooting Questions

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

Is the Water Heater Turned On?

It sounds simple, but always check if the water heater is actually turned on. With most RV appliances, it’s smart to start simple and work towards more complex checks. As obvious as it seems, begin with a check for power:

• For gas/electric models, the switch needs to be on for several minutes to heat the water in the tank.
• After turning it on, open the hot water faucet for 10-15 seconds to purge any cold water in the lines.

Tankless water heaters create “on-demand” hot water much more quickly, making them increasingly popular in modern RVs. Enjoy this video to learn more about on-demand RV water heaters and their benefits.

Is There Water in the Tank?

Next, check if the water heater tank is filled with water:

1. Turn off the gas and/or electric control switches.
2. Go outside and open the heater’s access cover.
3. Touch the pressure-temperature valve (P/T valve) to see if it’s warm or hot.
4. Use a coffee cup under the valve to check for hot water. If you hear air but no water comes out, the tank is likely empty.

If the water heater’s bypass valve is in winterize mode, adding cold water to a hot tank can cause significant damage. Wait 60-120 minutes for the tank to cool before changing the valve to the normal operation position and refilling the tank.

The cold water will crack the glass lining in a Suburban water heater tank, the flue tube that runs through the center of a Dometic RV water heater tank, and the electric heating element.

On pilot models, running the RV 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? The entire assembly must be replaced, 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.

How Long Has It Been Turned On?

Unless you have an on-demand or tankless water heater, heating the water takes time. Larger tanks (6-10 gallons, sometimes 12 or 16 gallons) require more time to heat the water.

• Tankless water heaters provide hot water within 5-10 seconds of turning on the switch.
• Gas/electric water heaters typically take 30-45 minutes to heat up.

Have You Run Out of Hot Water?

Standard RV water heater tanks hold about 6 gallons, which can provide 5-10 minutes of hot water depending on usage. Multiple showers back-to-back will require time for the tank to refill and reheat. Tankless water heaters, however, provide more consistent hot water but are still limited by factors like gray water tank capacity.

• 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 that must be filled and heated. However, the “unlimited hot water” that many tankless water heater manufacturers boast can be misleading because you will be 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 There 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, use these steps to check the propane supply and purge air from propane lines: 

• Ensure the valves on top of your propane containers are fully opened. 
• 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?

If your battery is drained, it won’t provide enough power for your water heater 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)

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.

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. Use this simple step to check for a faulty or reversed mixing valve: 

• 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.

Is the RV 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℉. So, if the cup is filled at the P/T valve, a thermometer reading of roughly 140℉ is normal. If drawing the water from a faucet, 120℉ is more likely. 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.

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

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 Is a Digital Multimeter? (And Why RVers Need One)
• RV Freezer Frosting Up?
• RV Water Pump Not Working?

Do you have questions about any of the water heater troubleshooting tips above? Let us know in the comments below.