RV Water Heater Anode Rod: When to Check It, Replacing It and Flushing the Tank

Does my water heater have an anode rod?

It depends on who made your heater, and one look at the tank tells you. Open the outside access door and look at the face of the tank. On a Suburban, the one large hex fitting at the front is the anode rod, and Suburban's tank water heater guide says it absorbs the corrosive action of hot water.

On an Atwood-style heater, the same opening holds a plain drain plug. Dometic, which took over the Atwood line, says its aluminum WH-series tank requires no anode rod and tells owners not to fit one. Grand Design's manual agrees that anode rods are for steel tanks only.

A tankless heater has nothing to check: Suburban confirms its IW60 uses no anode rod of any type. The rest of what a tank water heater needs is covered separately.

How often do I replace it?

Replace the rod by how much of it is left, checking it every 6 to 12 months. The published wear points sit close together:

• Suburban: check every 6 to 12 months, replace at more than 75 percent consumed.
• Grand Design: inspect yearly, change when the rod is down to about a quarter of its original size.
• Camco: for its own Atwood-style rod, replace when less than half the rod remains.

Suburban warns that RV antifreeze is very corrosive to the anode, which is why a bypass kit matters at season end. It also says to drain the tank whenever the RV is not in use.

What size do I need?

Buy the rod your heater's maker specifies, because rods differ in thread and length. A Suburban anode screws into a 3/4 inch opening, and Suburban tells owners not to replace it with any non-Suburban accessory part. The aftermarket rods in Camco's accessories catalog:

The two Atwood-style rows are for tanks Dometic says need no anode.

How do I drain and flush the tank?

Do this at least once a year, whether you are pulling an anode rod or a drain plug, as Dometic's WH-series manual advises.

1. Switch the heater off on both gas and electric, at the inside switches and at the breaker or element switch.
2. Let the water cool, or run a hot tap until it comes out cool, to avoid scalding.
3. Turn off the water supply: the pump and the city water connection.
4. Open a hot tap inside, then lift the lever on the temperature and pressure relief valve to release line pressure.
5. Remove the anode rod (1-1/16 inch socket on a Suburban) or the drain plug (Camco gives a 7/8 inch socket for its Atwood-style fitting). Stand clear of the stream.
6. If the water trickles, open the relief valve to let air in and poke a small gauge wire through the drain opening.
7. Flush the tank with an RV water heater flushing wand, or pump fresh water in for 90 seconds to stir up the sediment, because about two quarts stay in the bottom and hold most of the corrosive particles. Repeat until the water runs clear.
8. Inspect the rod. If it is past the wear point, fit the new one with a pipe thread sealant approved for potable water, such as Teflon tape, which Suburban says prevents a leak without interfering with the anode's protection. Snug it, do not force it: Camco's sheet calls for 7 to 8 lbs of torque on its own rod.
9. Close the relief valve, refill the tank with the hot taps open until the air is out, and only then switch the heater on. Running it without water damages the tank, controls or electric element, and is not covered by warranty.

Flushing matters because sediment on the tank bottom insulates the gas burner from the water, Suburban explains, overheating the tank bottom and damaging the steel and its glass lining. That shows up later as slow recovery or no hot water.

Common questions