# Replacing the Water Heater's Anode

We installed a new water heater 8 years ago, and since then I've ignored it. It's an indirect model, heated by the same gas boiler that heats our house, and it has done its job well. When I was [thinking about heat pumps](https://www.jefftk.com/p/running-the-numbers-on-a-heat-pump), however, I reread the manuals for our existing system and noticed that the [manufacturer recommends](https://www.heat-flo.com/storage/products/indirect-water-heaters/indirect-water-heaters-io-manual.pdf) checking the anode annually. The idea is that water will corrode metal, but prefers some metals to others, so if you put in a chunk of tasty sacrificial metal you lose that instead of the tank walls.

Once every eight years is not annual, but better late than never!

Since it had been quite a bit longer than anodes usually last, I preemptively ordered a new one. When it arrived I warned [people](https://www.jefftk.com/p/shared-house-setup) that I was going to be shutting off the hot water for a while, but as soon as I took off the insulating cap for the old anode it was clear I didn't have what I needed. It used a 1 3/4" hex head, recessed, and I didn't have any sockets close to that large. Neither did the hardware store: I had to order one.

[![](https://www.jefftk.com/one-and-three-quarters-hex-socket.jpg)](https://www.jefftk.com/one-and-three-quarters-hex-socket-big.jpg)

I think the manufacturer realized this was silly: the replacement anode came with a 1" head, and reading their [documentation](https://www.heat-flo.com/storage/products/indirect-water-heaters/indirect-water-heaters-io-manual.pdf) they switched to 1" in in 2021.

Once I had the right-sized parts I turned off the system, shut off the incoming water, opened a hot water tap to break the vacuum, hooked up a hose to the drain port, and got it draining. I went and did something else for a long while, and when I came back I started on the anode. The first problem was that the thermostat is immediately in front of the anode port:

[![](https://www.jefftk.com/thermostat-blocking-anode.jpg)](https://www.jefftk.com/thermostat-blocking-anode-big.jpg)

I needed to disassemble this more than I wanted to get it out of the way.

Once it was clear, it was hard to get the anode rotating. I needed a cheater bar (a pipe slipped over the breaker to extend it). When it came out I was surprised in two ways:

*   The old anode had been entirely consumed. Here is the new one and old one side-by-side:
    
    [![](https://www.jefftk.com/old-and-new-anodes.jpg)](https://www.jefftk.com/old-and-new-anodes-big.jpg)
    
*   Lots of water came out:
    
    [![](https://www.jefftk.com/water-leaving-via-the-anode-port.jpg)](https://www.jefftk.com/water-leaving-via-the-anode-port-big.jpg)
    

The problem was, I hadn't confirmed that the water heater had finished draining. An 80 gallon tank (two units, eight bedrooms, ten people) takes a long time to drain, and it was far from done. Luckily this is an unfinished basement with nothing that minds getting wet, and it all drains to a sump.

After the top finished draining out the wrong hole, and then the bottom finished draining out of the right hole, I cleaned anode port first with a wire brush and vinegar to remove mineral deposits andthen with an old toothbrush and water to remove anything left. I applied thread sealant, and put the new anode in. It was hard to get it seated right with the threads: it is long and reasonably heavy, and it really wants to pull down.

Once it was tight again, I turned the water back on to the tank. While it filled I used a hair dryer to dry out the thermostat. After a bit I turned the power back on. We have hot water again!

[![](https://www.jefftk.com/new-anode-installed.jpg)](https://www.jefftk.com/new-anode-installed-big.jpg)

I've seen myself a reminder for two years from now to check the anode again. By seeing how much has been eaten away in that time, I should be able to get a good estimate for when I should next replace it.

Overall this cost me:

*   $107.83: replacement anode
*   $16.19: 1 3/4" socket (3/4" drive)
*   $14.97: 1/2" drive breaker bar
*   $12.98: 1/2" to 3/4" socket adapter
*   $6.27: 1" socket (1/2" drive)
*   **$158.21: total**

Plus about three hours of my time, one in advance and two of actually doing the replacement. Since dealing with a water heater replacement is substantially more money and I enjoy doing this kind of thing, this seems worth it!

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