RV Water Heater Leak: Where to Check First

Most RV water heater leaks trace back to one of three spots: the pressure relief valve, the anode rod port (on Suburban-style tank heaters), or a cracked tank from freeze damage, and where the water is actually coming from changes both the fix and the urgency. This guide covers how to trace a leak to its source on both tank-style (Suburban, Atwood) and tankless RV water heaters, and which leaks are a quick fix versus a sign the tank itself has failed.

Check the Pressure/Temperature Relief Valve First

The P&T relief valve sits on top of or on the side of the tank and is designed to open automatically if internal pressure or temperature exceeds a safe threshold, which protects the tank from rupturing. It’s also the most common source of a slow drip, either because sediment has lodged under the valve seat keeping it from sealing fully, or because the rubber seal has simply aged and hardened. Lift the test lever briefly to flush any trapped sediment through; if it still drips afterward, the valve itself needs replacing, a straightforward swap that costs under 20 dollars in parts.

Check the Anode Rod and Drain Plug (Suburban Tanks)

Suburban-brand water heaters use a sacrificial anode rod, often built into the drain plug itself, that corrodes over time to protect the steel tank from rusting through. Leaking around this plug usually means the sealing washer has degraded, or the plug simply wasn’t torqued to the correct spec (typically hand-tight plus a partial turn, not wrench-tight, since overtightening can crack the plug or strip the tank’s threaded boss). Atwood/Dometic aluminum tanks don’t use a separate anode rod, if you have an Atwood-brand heater and it’s leaking from that area, the issue is more likely the drain plug’s seal alone.

Check Fittings and Connections Where Water Lines Enter

Follow the hot and cold water line connections into the heater; RV plumbing uses plastic push-fit or compression fittings that can loosen from the constant vibration of driving, which is a different failure mode than household plumbing sees. A leak here often shows up as dampness along the water lines rather than pooling directly under the tank, so trace visible wet spots back along the pipe run before assuming the tank itself is the source.

A Cracked Tank Usually Means Freeze Damage

If water is coming from a crack or split in the tank body itself rather than a fitting or valve, the most common cause in an RV is a freeze event, water left in the tank during winter storage without proper winterization expands as it freezes and can crack the tank irreversibly. This is not repairable; a cracked tank means replacing the entire water heater unit. This is exactly why RV winterization procedures emphasize fully draining and bypassing the water heater (not just the fresh tank) before any freezing temperatures, one missed step there is the single most common cause of a cracked RV water heater tank.

Tankless RV Water Heaters: Different Leak Points

Tankless units (like the Truma or some newer Suburban models) don’t have a large tank to crack, but they do have a heat exchanger, inlet/outlet fittings, and often an internal check valve or mixing valve, any of which can develop a leak from mineral scale buildup, a failed gasket, or the same freeze-related cracking if the heat exchanger wasn’t drained properly. Because these leaks are often internal to the unit rather than an external fitting, a tankless heater leaking from inside the housing generally needs a technician rather than a DIY teardown, unlike the more accessible relief valve and drain plug on a tank-style unit. The diagnostic order is similar to troubleshooting a residential water heater that won’t heat: rule out the simple external parts (valves, fittings, seals) before assuming the tank or heat exchanger itself has failed.

Frequently Asked Questions

Is it safe to keep using an RV water heater that’s leaking from the relief valve?

A slow drip from the relief valve isn’t an immediate safety hazard, but it wastes water and can indicate sediment buildup or a failing seal. Replace the valve promptly rather than ignoring an ongoing drip.

How do I know if my RV water heater tank actually cracked from freezing?

Water pooling directly under the tank body itself, not from a fitting, valve, or plug, especially after a season the RV was stored without full winterization, points strongly to a frozen and cracked tank, which requires full replacement.

Do I need to winterize the water heater separately from the rest of the RV plumbing?

Yes. The water heater has to be drained and bypassed on its own (using its bypass valve so antifreeze doesn’t fill the tank unnecessarily), it isn’t automatically emptied just because the fresh water tank and other lines have been drained.