Water Heater Hot When Empty - No Safety Protection Issue

The Quick Answer

You're absolutely right to be concerned - running your RV water heater dry is dangerous and can cause serious damage or even fire. Most RV water heaters do NOT have automatic dry-fire protection, which is why your heater was heating up even though it was empty. You did the right thing by turning it off at the electrical panel. Since you've been keeping it plugged into shore power with the dehumidifier, the water heater has likely been cycling on and off whenever the thermostat called for heat, even without water in the tank. This could have damaged the heating element and created a fire hazard.

What's Causing This

The root cause is that most RV water heaters, especially older models, lack built-in dry-fire protection systems. When you drain your RV for storage or winterization, the water heater tank empties but the electrical connection remains active if you're plugged into shore power. The thermostat doesn't know there's no water - it just sees that the temperature isn't reaching the set point and keeps energizing the heating element.

Running the heating element without water causes it to overheat rapidly since there's no water to absorb and dissipate the heat. This can burn out the element, damage the tank lining, or in worst cases, cause the element to glow red-hot and potentially ignite nearby materials. The fact that you've been doing this for storage while running a dehumidifier means this has been happening repeatedly over time.

Many RV owners make this same mistake because residential water heaters typically have better safety features. It's a common but dangerous oversight that can lead to costly repairs or catastrophic damage.

Tools You'll Need

To inspect for damage and prevent future issues, you'll need:

• Multimeter for testing electrical continuity
• Flashlight or headlamp for tank inspection
• Basic hand tools (screwdrivers, socket set)
• Water heater element wrench (if replacement needed)
• New heating element (possibly 120V, 1500W - check your specific model)
• Thread sealant or new element gasket
• thermal cutoff switch or dry-fire protection kit if available for your model

Step-by-Step Fix

First, inspect for damage by removing the water heater access panel and visually checking the heating element and surrounding area for signs of burning, discoloration, or warping. Look for any melted wiring or damaged insulation around the element area.

Next, test the heating element with your multimeter. Set it to resistance mode and test across the element terminals - you should get a reading of approximately 9.6 ohms for a typical 1500W/120V RV element (check your specific wattage rating as readings will vary). No reading (infinite resistance) means the element is burned out and needs replacement. If the element tests good and your water heater is equipped with an ECO (Energy Cut Off) switch, check that its reset button hasn't tripped.

If you need to replace the element, drain any remaining water, disconnect the electrical wires, and use the element wrench to remove the old one. Install the new element with the gasket (do not use thread sealant as this can interfere with proper gasket sealing), and reconnect the wiring. Make sure all connections are tight and properly insulated.

For future prevention, install a water heater bypass valve system that allows you to completely isolate the water heater during storage. Also consider adding an aftermarket dry-fire protection switch if one isn't built into your system. Always turn off the water heater breaker when draining your RV, regardless of whether you're keeping shore power connected.

When to Call a Pro

Call a professional RV technician if you find extensive damage to the tank, wiring, or surrounding structure. Signs include warped or discolored tank walls, melted wiring insulation, or burn marks on nearby wood or plastic components. These indicate potential fire damage that needs expert assessment.

Also seek professional help if you're uncomfortable working with 120V electrical systems, if the water heater is gas/electric combo unit (more complex), or if you discover the tank itself is damaged. A professional can also install permanent dry-fire protection systems and ensure all electrical connections meet code requirements.

Don't attempt repairs if you smell gas around a gas water heater or if there are any signs of structural damage to your RV from overheating. These situations require immediate professional attention and may involve insurance claims.