Replacing an RV water heater is one of the more satisfying DIY jobs you can tackle on your rig. It's not overly complicated, the parts are readily available, and doing it yourself saves a significant amount in labor costs. Most replacements can be completed in 2–3 hours with basic hand tools.
This guide covers tank-to-tank water heater replacement — the most common swap RV owners make. If you're considering switching to a tankless unit instead, the installation process is more involved and we cover that separately. For a straight tank replacement, read on.
Tools and Materials You'll Need
- Replacement RV water heater (confirm model fits your existing cutout)
- Screwdrivers (Phillips and flathead)
- Adjustable wrench or channel-lock pliers
- Pipe thread sealant tape (Teflon tape)
- Utility knife
- Butyl tape or self-leveling lap sealant
- Drill and bits (if new screw holes are needed)
- Multimeter (optional, for testing connections)
- Bucket and towels (for draining residual water)
Safety Precautions Before You Start
- Turn off all propane at the tank before doing anything — not just at the appliance
- Disconnect shore power or turn off the inverter if your water heater has an electric element
- Let the unit cool completely if it was recently running — the tank and burner assembly get very hot
- Relieve water pressure by opening a hot water tap inside the RV before disconnecting water lines
- Never work on a live gas line — if you smell propane at any point, stop and ventilate before continuing
Step-by-Step: How to Replace an RV Water Heater
Step 1: Drain the Old Water Heater
Turn off your water pump and city water supply. Open a hot water faucet inside the RV to release pressure. Remove the drain plug or anode rod from the bottom of the water heater (located on the exterior access panel) and allow the tank to drain completely. Have a bucket and towels ready — there will be residual water.
Step 2: Shut Off the Propane Supply
Turn off the propane at the tank. Then locate the gas line connection at the water heater — typically a flare fitting or compression fitting on the burner assembly. Do not disconnect yet; just confirm you know where it is.
Step 3: Disconnect the Water Lines
Using your wrench, disconnect the cold water inlet and hot water outlet lines from the water heater. These are typically 1/2-inch fittings. Wrap disconnected fittings with a rag to catch any remaining drips. If your RV has a bypass valve system, make sure it's in bypass mode before disconnecting to prevent water from flowing back.
Step 4: Disconnect the Gas Line
With propane fully shut off, carefully disconnect the gas supply line from the burner assembly. Use two wrenches — one to hold the fitting on the heater, one to turn the line fitting — to avoid stressing the gas line. Set the line aside carefully.
Step 5: Disconnect the Electrical Connections
If your water heater has a 120V electric element, disconnect the AC wiring at the junction box on the unit. For DSI (direct spark ignition) models, disconnect the 12V DC wiring harness. Take a photo before disconnecting so you remember which wires go where.
Step 6: Remove the Exterior Door and Trim
Unscrew and remove the exterior access door and any trim ring around the water heater opening. Set these aside — you may be able to reuse them depending on the new unit's dimensions.
Step 7: Remove the Old Water Heater
The water heater is typically held in place by screws around the flange or by mounting brackets inside the bay. Remove all fasteners and carefully slide the unit out. RV water heaters are heavy — have a helper on hand, or at minimum something to rest it on as it comes out. Inspect the opening for any rot, water damage, or debris before installing the new unit.
Step 8: Prepare the New Water Heater
Unbox the new unit and compare its dimensions to the opening. Most standard RV water heaters are designed to fit a 16.5" x 16.5" cutout, but always verify. Apply fresh Teflon tape to all threaded water fittings on the new unit — wrap clockwise 2–3 times for a good seal.
Step 9: Apply Sealant Around the Opening
Before sliding the new unit in, apply a bead of butyl tape or self-leveling lap sealant around the exterior opening to create a watertight seal between the unit flange and the RV sidewall. This step is critical — skipping it leads to water intrusion and wall damage over time.
Step 10: Slide In the New Water Heater
Carefully slide the new unit into the opening. Make sure it seats flush against the exterior wall. Secure it with the provided screws or mounting hardware, working around the flange evenly to ensure a tight seal.
Step 11: Reconnect the Water Lines
Reconnect the cold inlet and hot outlet water lines. Hand-tighten first, then snug with a wrench — do not overtighten plastic fittings. Double-check that cold goes to cold and hot goes to hot (they're typically labeled on the unit).
Step 12: Reconnect the Gas Line
Reconnect the propane supply line to the burner assembly using two wrenches. Once connected, apply a small amount of soapy water to the fitting and briefly turn on the propane to check for bubbles — any bubbling indicates a leak. Tighten further if needed, and do not proceed until the connection is confirmed leak-free.
Step 13: Reconnect the Electrical Connections
Reconnect the 12V DSI wiring harness and/or the 120V AC wiring, referencing the photo you took earlier. Ensure all connections are secure and no bare wires are exposed.
Step 14: Reinstall the Exterior Door and Trim
Reattach the exterior access door and trim. If the new unit came with its own door, use that. Apply a thin bead of lap sealant around the trim ring where it meets the RV sidewall for added weather protection.
Step 15: Fill the Tank and Check for Leaks
Turn your water supply back on (pump or city water) and allow the tank to fill completely. You'll know it's full when water flows steadily from the open hot water tap inside the RV. Close the tap, then inspect all water fittings on the heater for drips. Tighten as needed.
Step 16: Light the Water Heater and Test
Turn the propane back on at the tank. Follow the manufacturer's lighting instructions — most DSI models light automatically when you flip the switch on the interior control panel. Allow 20–30 minutes for the water to heat, then test at a hot tap. You're done.
Common Mistakes to Avoid
- Skipping the sealant: A dry-fit installation without sealant will eventually leak — don't skip this step
- Not purging air from the tank: Always fill the tank completely before lighting the heater. Firing a dry tank damages the element and can crack the tank
- Overtightening plastic fittings: Hand-tight plus a quarter turn is usually enough — plastic threads strip easily
- Skipping the leak test: Always check the gas fitting with soapy water before walking away
- Assuming dimensions match: Even same-brand replacements can have slightly different dimensions — measure the cutout before ordering
Frequently Asked Questions
How long does it take to replace an RV water heater?
Most DIY replacements take 2–3 hours for someone with basic mechanical experience. First-timers should budget closer to 3–4 hours to allow time for reading instructions and double-checking connections.
Do I need a plumber to replace an RV water heater?
Not for a standard tank-for-tank swap. The water and gas connections are straightforward and well within DIY range. If you're switching to a tankless unit rather than replacing like-for-like, the venting and cutout requirements are different — that's a job worth consulting a certified RV technician on, or at minimum researching your specific tankless model's installation requirements before starting.
Can I replace a 6-gallon RV water heater with a 10-gallon unit?
Only if the 10-gallon unit fits your existing cutout — which it typically won't without modification. Most 10-gallon units require a larger opening. Measure carefully before ordering.
How do I know what size RV water heater to buy?
Measure your existing cutout opening and note the brand and model number of the old unit. Most standard RV water heaters fit a 16.5" x 16.5" opening. Cross-reference the model number with our parts guide to find a compatible replacement.
What sealant should I use around an RV water heater?
Butyl tape works well for the initial seal around the flange. Self-leveling lap sealant (such as Dicor) is ideal for finishing the trim ring and any gaps. Avoid silicone — it doesn't bond well to most RV exterior surfaces and is difficult to remove later.
Get Your Replacement Water Heater at The RV Surplus
We carry Suburban and Atwood/Dometic RV tank water heaters at discount prices, with free shipping to the continental U.S. Prefer to make the switch to tankless? We carry those too — just be sure to review the installation requirements before ordering.
Shop RV Water Heaters at The RV Surplus →
Not sure which unit fits your rig? Call or text us at 574-218-0549 and we'll help you match the right replacement. You can also check our RV Water Heater Troubleshooting Guide if you're still deciding between a repair and a full replacement.
Already have your new unit? Follow the steps above and you'll have hot water running again before the end of the day.