RV Water Heater Leaking From the Bottom

The Short Answer: A leak at the bottom of an RV water heater tank is usually the drain plug or, on Suburban heaters, the anode rod, which also serves as the drain. Both seal with threads and wear with every removal. If the plug area is dry but water still appears at the bottom of the tank, the tank has likely corroded through and the heater needs replacing.

Know which tank you have

The badge inside the outside access door tells you.

• Suburban tanks are steel with a porcelain lining. Suburban’s manual says the tank is protected by a magnesium or aluminum anode rod, that the tank is drained by removing that anode, and that the anode should be replaced yearly (more often with water high in iron or sulfate). Running without proper anode protection shortens tank life and voids the tank warranty.
• Atwood/Dometic tanks are aluminum, do not use an anode rod, and have a plastic drain plug.

Bottom-of-tank leak sources

Drain plug or anode threads. Weeping around the plug is the most common bottom leak. Causes include a worn or missing seal, threads damaged by over-tightening, debris on the sealing surface, or, on Suburban, an anode that has been eaten away. Replacement is routine once the heater is off, cool, and drained.

A corroded tank. On a Suburban, an anode left in place too long stops protecting the tank, and corrosion attacks the steel. Rust at the bottom seam, rusty hot water, and dampness on the outside of the tank with the plug dry point to tank failure. Aluminum tanks fail too, usually after many years, sometimes from freeze damage.

Freeze damage. A tank that was not drained before freezing weather can split. Suburban’s manual says the heater must be drained if the RV is stored in winter.

How to check, step by step

1. Turn off the gas and electric switches for the water heater, the pump, and city water. Let the tank cool.
2. Open a hot faucet inside to relieve pressure.
3. Dry the plug and the bottom of the tank face.
4. Turn the water back on without heating, then watch the plug and the tank seams.

If the drip is at the plug, a new plug or anode with fresh thread sealant usually solves it. Use the anode or plug specified for your heater; Suburban warns against substituting non-Suburban parts in the anode opening. On Atwood/Dometic tanks, tighten a plastic plug only as much as needed; cracking it or the tank threads makes the problem worse.

Winterizing and the anode

Suburban notes that RV antifreeze is corrosive to the anode. Its manual recommends using the bypass kit to keep antifreeze out of the water heater, or, without a bypass, removing the anode for the winter and installing a 3/4-inch drain plug in its place. Skipping this step is one reason anodes and tank threads wear out early.

Replace or repair

Plugs, anodes, and seals are minor repairs. A tank leak means a new water heater. Do not use sealants or patches on a pressurized tank, and do not run the burner or electric element if water is reaching the controls or burner area.

Related: RV water heater leaking outside, RV relief valve dripping, and Suburban RV water heater leaking.

Frequently Asked Questions

Q: How do I know if my Suburban anode needs replacing? A: Remove it when draining the tank. Suburban says to replace it yearly, and sooner if it is mostly eaten away. A rod worn down to its core wire is long overdue.

Q: Should I put an anode in an Atwood tank? A: No. Atwood/Dometic aluminum tanks are designed without one. Use only the plug made for that tank.