RV Hot Water Heater: Complete Guide for Homeowners

An rv hot water heater is a small, rugged appliance that does a surprisingly big job — delivering hot showers, warm dishwater, and comfort on the road from a tank that’s often just 6 or 10 gallons. Whether you’re troubleshooting a unit that won’t light, deciding between tank and tankless for an upgrade, or getting ready to winterize, understanding how these compact heaters work will save you cold showers and expensive service calls. Here’s the complete rundown for RV owners.

How an RV Water Heater Differs From a Home Unit

A residential heater assumes constant utility power, city water pressure, and a permanent install. An RV heater has to run off multiple energy sources, tolerate vibration and freezing, and work with a pump-fed water system. Most RV units mount through an exterior sidewall with an access door, and they’re built to switch between propane (LP gas) and 120V electric — or use both — depending on whether you’re boondocking or plugged into shore power.

Capacities are small: 6-gallon and 10-gallon tanks are standard, with 16-gallon units on larger rigs. That’s why RVers learn “Navy showers” — the tank recovers, but not instantly.

The Main Types

Tank (Storage) Heaters

The traditional choice, dominated by two brands: Suburban and Atwood (now Dometic). They store 6 to 16 gallons and heat via a propane burner, a 120V electric element, or both. Suburban tanks are steel with an anode rod; Atwood/Dometic tanks are aluminum and don’t need one. Recovery on a 6-gallon tank runs about 20 minutes on gas.

Tankless (On-Demand) Heaters

An increasingly popular upgrade. RV tankless units like the Girard GSWH-2 or Furrion heat water instantly and endlessly off propane, so no more waiting for a tank to recover between showers. They save weight and space and eliminate the winterizing hassle of a stored tank — but they need steady water flow and pressure to fire, and they cost more ($350 to $700 versus $250 to $450 for a comparable tank unit).

Gas, Electric, or Both

Your energy source dictates when and where you get hot water:

• Propane (LP gas): Works anywhere, even off-grid. Fast recovery. Uses a small amount of propane and a 12V spark to ignite.
• 120V electric: Free hot water when you’re on shore power at a campground, but slow to recover and useless when boondocking.
• Gas/electric (DSI dual): The best of both — run electric at the campground, propane in the wild. Most modern RV heaters offer this.

If you’re shopping, a dual gas/electric unit gives you the most flexibility for the small price difference.

Understanding Bypass Mode

Every RV water heater setup should include a bypass valve — three valves (or one summer/winter valve) behind the tank that let you route water around the heater. You use bypass for two things: winterizing (so antifreeze doesn’t fill and waste 6 gallons in the tank) and isolating the tank for service. Learn where your bypass valves are before you need them; hunting for them in a cold campground with a broken heater is no fun.

Common Problems and Fixes

Most RV hot water heater failures trace to a handful of causes you can often fix yourself:

1. Won’t ignite on gas: Check for propane supply, a tripped DSI lockout (reset by cycling the switch), a dirty burner tube (spiders love these — clean with compressed air), or a weak 12V battery.
2. No heat on electric: Test the heating element and the thermal cutoff / high-limit reset (a small button near the element).
3. Lukewarm water: A failing thermostat or a partially closed bypass valve mixing cold water in.
4. Leaking: Check the drain plug/anode rod, the T&P valve, and the tank seams. A weeping T&P valve on heat-up can be normal expansion; a constant drip means a bad valve.
5. Rotten-egg smell (Suburban): A depleted anode rod reacting with the water — replace it.

Keep spare parts on hand: an anode rod (Suburban), a spare thermal cutoff, and a drain plug. They’re cheap and save a trip in the middle of nowhere.

The Anode Rod (Suburban Only)

Suburban steel tanks use a sacrificial magnesium or aluminum anode rod that also serves as the drain plug. It corrodes to protect the tank, so inspect it each season and replace it when it’s more than 75% consumed — usually annually with regular use. Aluminum-zinc anodes cut the rotten-egg smell in problem water. Atwood/Dometic aluminum tanks need no anode; installing one in them can actually cause problems, so know which tank you have.

Winterizing Your RV Water Heater

Freeze damage is the number-one killer of RV heaters, and it’s completely preventable. Before the first hard freeze:

1. Turn off the heater and let the water cool completely.
2. Turn off the water supply and release tank pressure by opening a hot tap and the T&P valve.
3. Remove the drain plug / anode rod and drain all 6 to 10 gallons.
4. Set the bypass valves so antifreeze skips the tank.
5. Reinstall the plug (or replace the anode), then pump RV antifreeze through the rest of the plumbing.

Never run antifreeze into the tank itself — it wastes gallons and is hard to flush out in spring.

Upgrading and Buying Tips

If your old tank unit is tired, the tankless upgrade is tempting for endless hot showers, but confirm your water pump maintains the flow the unit needs to fire consistently. For a straight replacement, match the new unit’s dimensions to your existing wall opening — Suburban and Atwood/Dometic cutouts differ slightly, and swapping brands may mean modifying the opening or buying an adapter trim kit. Whatever you choose, a well-maintained rv hot water heater — flushed each season, anode checked, and properly winterized — will deliver reliable hot water on the road for a decade or more.

Flushing and Seasonal Maintenance

Sediment builds in an RV tank just like a home unit, and in a 6-gallon tank it eats capacity fast. Once a season, flush it:

1. Turn off the heater and water supply, and let the tank cool completely.
2. Relieve pressure by opening a hot faucet, then open the T&P valve.
3. Remove the drain plug or anode rod and let the tank drain.
4. Use an inexpensive RV tank rinser wand (or a flush with the water pump) to blast out sediment through the drain hole.
5. Inspect the anode (Suburban), reinstall the plug with fresh Teflon tape, and refill before firing.

While you’re at it, check the burner tube for spider webs and dust — a quick blast of compressed air here prevents most no-ignition headaches — and confirm the exterior vent isn’t blocked by mud-dauber nests.

Getting More Hot Water on the Road

Six or ten gallons goes quickly, so RVers learn to stretch it. Run the heater on both gas and electric at once (if your unit supports it) for faster recovery when you’re plugged in. Take “Navy showers” — wet down, shut the water, soap up, then rinse — to make a tankful cover multiple people. A low-flow RV showerhead with a shutoff button helps enormously. And plan the sequence: shower before doing a sink full of dishes rather than draining the tank on dishes first. If endless hot water matters to you, that’s the case for upgrading to an on-demand tankless unit.

Frequently Asked Questions

How do I know if I have a Suburban or Atwood/Dometic heater?

Check the access door or the tank. Suburban tanks are steel and use an anode rod (which doubles as the drain plug); Atwood/Dometic tanks are aluminum with a plastic drain plug and no anode. It matters — never add an anode to an aluminum tank.

Why won’t my RV water heater light on propane?

Most often a tripped DSI lockout (cycle the switch to reset), no propane flow, a low 12V battery, or a burner tube clogged with spider webs. Work through those before assuming a failed board.