Thursday, November 30, 2023


Ask Dave: When do you replace the water heater anode?

Dear Dave,
How do you know when it’s time to replace the water heater anode? —Timothy

Dear Timothy,
You indicate the unit is a 2021 Rapid, which means it’s probably only one or maybe two years old. And since it has an anode rod, the water heater is a Suburban model. The anode rod acts as a sacrificial metal for the aggressive water action which creates protection for the tank. It should be inspected every year, and Suburban recommends replacing it when 75% of the rod has deteriorated.

This is a new anode rod.

This is the picture of yours.

And this is a diagram for reference from the Suburban Service Manual.

Although most of your anode rod is not at the 75% deterioration rate, the first inch is what concerns me. What could happen is the thin metal at this point could break inside the tank and would be almost impossible to get out.

Deterioration of an anode rod depends on several factors

Deterioration of the anode rod will differ depending on the quality of water, frequency of use, and maintenance. I would recommend replacing the anode rod with a new Suburban replacement. Other after-market rods, especially add-on electric heating element rods, can cause problems and void the warranty.

Before installing the new anode rod, I would also recommend to flush out of the tank using a flush wand like this one.

This will help flush out any sediment that could have settled in the bottom of the tank, as the drain is about 1.5” above the bottom. If the anode rod breaks off, this and the sediment at the bottom of the tank insulates the water from the heating source so it will not run as efficiently. It will also slow the heating process and could damage the tank’s glass lining by overheating the bottom of the tank.

If you are not using a filter at the water source, I would recommend either getting a Shurflo in-line filter, or a larger residential version that you can get a drop-in cartridge to hopefully filter out some of what is aggressively deteriorating the anode.

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

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Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.



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Steve (@guest_174929)
1 year ago

Dave, The center core of the anode rod is steel and not “sacrificial” magnesium. I have seen some of my rods almost all just the steel core (overdue for a change) but no deterioration of the center core. I have never thought of it breaking off inside the tank but I don’t have your experience. Thanks for the heads up.

DAVE TELENKO (@guest_174923)
1 year ago

Hi Dave, I have a 2017 Forest River 34QS DP. Ours is a Atwood on demand water heater, does it have an anode?

DAVE TELENKO (@guest_174972)
1 year ago
Reply to  Dave Solberg

Hey Dave, thanks for extra research on my Atwood!

Oscar Thomson (@guest_175014)
1 year ago
Reply to  Dave Solberg

The galvanic series from high school chemistry says: Magnesium, aluminum, zinc, iron, in that order. Thus, magnesium anodes will protect all elements following. Zinc will protect iron. Similarly, if you use a zinc anode in an aluminum tank, the tank will be the anode and its’ life will shorten. If you read the Camco box holding a magnesium anode it says for Atwood water heaters.

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