Quick answer: most RVs have a 6- or 10-gallon tank water heater that runs on propane, 120-volt electricity or both, while some newer units are tankless and heat water on demand. Always make sure the tank is full of water before turning on the electric element, because running it dry can burn it out. Steel tanks typically use a sacrificial anode rod that should be inspected regularly, while aluminum tanks generally do not. Drain the tank before storage, and use the bypass valves when winterizing so antifreeze does not fill the heater. Hot water from an RV heater can scald, so test it before showering children.
Hot water turns an RV from a shelter into a home on wheels. A warm shower after a dusty hike or hot water for dishes makes camping more comfortable, but an RV water heater is a little different from the one in a house. It is smaller, it may run on more than one energy source, and it needs seasonal care that a home unit does not.
This guide explains how RV water heaters work and how to use and maintain them safely. It is part of our RV and van camping guide, which covers RV systems, campgrounds and travel basics.
Sources: RV water heater manufacturer owner’s manuals for tank and tankless models; RV Industry Association (RVIA) consumer resources; U.S. Consumer Product Safety Commission (CPSC) guidance on tap water scalds; U.S. Department of Energy (energy.gov) water heating basics. Procedures vary by model, so always follow your own manual. Checked October 2026.
How an RV Water Heater Works
A tank-style RV water heater is an insulated container, usually holding 6 or 10 gallons, connected to the RV’s fresh water system. Cold water enters the tank, is heated by a propane burner, an electric element or both, and leaves through the hot water line to the faucets and shower.
Because the tank is small, hot water runs out faster than at home. A 6-gallon tank may provide only a few minutes of hot shower water before it needs time to recover. That is why many RVers take “navy showers,” turning the water off while soaping up.
Types of RV Water Heaters
| Type | Heat source | Pros | Cons |
|---|---|---|---|
| Propane-only tank | Propane burner | Fast recovery; works off-grid | Uses propane; needs ignition |
| Electric-only tank | 120-volt element | Quiet; no propane use | Needs shore power or generator; slower |
| Dual propane/electric tank | Both | Flexible; can run both for faster recovery | More parts to maintain |
| Tankless (on demand) | Propane, sometimes with electronic controls | Continuous hot water; no tank to drain fully | Needs adequate water flow; higher cost |
Ignition types on propane units
Older RV water heaters use a pilot light that you light by hand. Most modern units use direct spark ignition (DSI), which lights the burner automatically when you flip a switch inside the RV. If the burner fails to light after several tries, a DSI unit locks out and needs to be reset.
Tankless models
Tankless units heat water as it flows, so they do not run out of hot water. They need a minimum flow rate to fire, and some campers notice temperature swings at low flow. They still need winterizing according to the manufacturer.
Before You Turn It On: Fill the Tank
The most important rule in most manufacturer manuals is to make sure the tank is full before turning on the heat. An electric element that is switched on in an empty tank can burn out quickly.
To fill the tank:
- Make sure the bypass valves are in the normal position, so water flows into the heater.
- Turn on the water pump or connect city water.
- Open a hot water faucet and let it run until water flows steadily with no sputtering. Air leaving the line means the tank is filling.
- Close the faucet, then turn on the heater.
Turning the Water Heater On
Propane
- Open the propane supply at the tank.
- Switch on the water heater from the control panel (for DSI models) or light the pilot according to the manual.
- Listen for the burner. You may hear a whoosh from the outside access panel.
Our guide to RV propane safety covers leak checks and detectors.
Electric
- Connect to shore power or run the generator.
- Flip the electric switch, usually located on the heater’s outside panel or inside the RV.
Many owners run both at once in the morning for faster recovery, then switch to electric only when hooked up. Our guide to RV hookups explains how much power your campsite supplies.
Water Temperature and Scald Safety
Many RV water heaters have fixed thermostats that heat water well above typical home settings, according to manufacturer manuals. The U.S. Consumer Product Safety Commission recommends setting home water heaters to 120°F to reduce the risk of scald burns, especially for young children and older adults, whose skin burns more easily.
Practical ways to stay safe in an RV:
- Test water temperature with your hand before a child bathes or showers.
- Mix cold water at the faucet.
- Consider a mixing valve, which some owners install to blend hot and cold water automatically.
- Turn off the water heater when it is not needed.
The Pressure-Temperature Relief Valve
Every tank water heater has a pressure-temperature (P&T) relief valve, usually on the outside panel. It opens to release water if the pressure or temperature inside the tank becomes too high. Manufacturer manuals note that occasional dripping can be normal as water expands during heating, especially if the air pocket at the top of the tank has been lost. Constant dripping or spraying is a sign of a problem that needs attention.
Never plug or cap the relief valve. It is a critical safety device.
Anode Rods
Steel-tank RV water heaters typically use a sacrificial anode rod made of magnesium or aluminum. The rod corrodes instead of the tank, extending the tank’s life. Aluminum tanks generally do not need an anode rod, according to manufacturer manuals, though they use a drain plug in the same location.
Checking the anode rod
- Turn off the heater and let the water cool.
- Turn off the water supply and relieve pressure by opening a hot faucet or lifting the relief valve lever carefully.
- Remove the anode rod with a socket wrench.
- Inspect it. If much of the metal has been eaten away, replace it. Many manuals suggest replacing when about 75 percent of the rod is gone.
Check the anode rod at least once a year, or more often if you use the RV heavily or camp in areas with hard water.
Draining and Flushing the Tank
Draining the tank removes sediment and is essential before winter storage.
- Turn off the water heater at both the propane and electric switches.
- Let the water cool completely.
- Turn off the water pump and city water.
- Open a hot faucet and release pressure at the relief valve.
- Remove the drain plug or anode rod from the outside panel. Water may come out quickly.
- Flush the tank, if your manual allows it, with a tank rinsing wand to wash out sediment.
- Reinstall the plug or rod using plumber’s tape on the threads if your manual recommends it.
Some RVers flush the tank every few months, especially when camping in areas with mineral-rich water.
Bypass Valves and Winterizing
Most RVs have a set of bypass valves near the water heater. In normal use, water flows into the heater. In bypass mode, water and antifreeze skip the heater. Bypassing saves gallons of RV antifreeze and keeps it out of the tank.
The basic winterizing steps for the water heater are:
- Drain the tank fully.
- Set the bypass valves to bypass.
- Pump RV antifreeze through the rest of the plumbing.
Our full guide to winterizing an RV walks through the entire process. When you de-winterize in spring, remember to switch the bypass back to normal and refill the tank before turning the heater on.
Propane Water Heaters While Driving or Fueling
Many RVers turn off propane appliances, including the water heater, before refueling, because an open flame near gasoline vapors at a pump is dangerous. Many fuel stations post rules requiring all pilot lights and burners to be turned off. Some tunnels and bridges also restrict propane use. Follow posted rules and your manufacturer’s instructions.
Making Hot Water Last on a Small Tank
A small tank means planning showers and dishes around recovery time. These habits stretch a 6- or 10-gallon tank further.
Space out showers. Waiting 20 to 30 minutes between showers, depending on the heater and heat source, gives the tank time to reheat. Running propane and electric together, where the manual allows it, shortens that wait.
Use a low-flow showerhead with a shut-off button. Many RV showerheads include a small valve that pauses the flow while you soap up, so you use hot water only while rinsing. Because the hot and cold valves stay set, the temperature is close to where you left it when you resume.
Wash dishes in a basin rather than under running water. Heating a small pot of water on the stove for dishes is another way to save the tank for showers.
Insulate where you can. Some owners add insulation to exposed hot water lines in cold weather, which reduces heat loss between the heater and the faucet. Keeping the RV warm also helps, since the tank loses less heat to the surrounding compartment.
Finally, conserve water as well as heat when you are boondocking. The fresh and gray tanks often run out before the propane does, so shorter showers protect your whole trip. Our guide to dumping RV tanks covers the other side of the water system.
Common Problems and Fixes
| Problem | Possible cause | What to try |
|---|---|---|
| No hot water on electric | Breaker off, switch off, burned-out element | Check breaker and switch; test element |
| Propane burner won’t light | Propane off, air in line, lockout, dirty igniter | Run another propane appliance to purge air; reset |
| Rotten egg smell | Bacteria reacting with the anode rod | Flush tank; sanitize the system per manual |
| Relief valve dripping | Heat expansion; lost air pocket | Restore air pocket per manual; check valve |
| Popping or rumbling | Sediment buildup | Drain and flush the tank |
| Water runs hot then cold quickly | Small tank or bypass partly open | Check bypass valves; give tank time to recover |
Restoring the Air Pocket
Several manufacturers describe an air pocket at the top of the tank that cushions water expansion. Over time, that air can be absorbed, leading to more relief valve drips. Many manuals describe restoring it by turning off the heater and water supply, opening a hot faucet and lifting the relief valve lever until water stops flowing, then closing everything and refilling. Follow the steps in your own manual.
Daily Habits That Help
- Turn off the heater when not needed to save propane and electricity.
- Fill the tank before every heating session after storage.
- Run both heat sources briefly for fast recovery before showers, if your unit allows.
- Keep the outside panel clean and check for insect nests, which can block burner tubes.
- Note your heater’s model number in your RV notebook for parts and manuals.
Common Mistakes
- Turning on the electric element with an empty tank.
- Forgetting the bypass valve after winterizing in spring.
- Ignoring the anode rod for years on a steel tank.
- Plugging a dripping relief valve.
- Leaving propane burners on at the fuel pump.
These same habits fit into the broader first-trip lessons in our guide to RV first trip mistakes.
Frequently Asked Questions
How long does an RV water heater take to heat up?
It depends on tank size and heat source. Propane generally heats a tank faster than the electric element. Running both, where allowed, speeds recovery.
Can I run my RV water heater on propane and electric at the same time?
Many dual-mode units allow it for faster recovery. Check your manufacturer’s instructions.
Why is my RV water heater relief valve dripping?
Occasional dripping can happen as water expands during heating. Constant dripping can mean the air pocket has been lost or the valve needs attention.
Does every RV water heater have an anode rod?
No. Steel tanks typically use a sacrificial anode rod, while aluminum tanks generally do not.
How do I drain an RV water heater?
Turn off all heat sources, let the water cool, shut off the water supply, relieve pressure and then remove the drain plug or anode rod from the outside panel.
Do I need to drain my water heater to winterize?
Yes. Drain the tank and use the bypass valves so antifreeze does not fill the heater.
