anode rods

[pasadena_commut]

Let's talk anode rods. I am aware that anode rods prevent corrosion to the water heater tank. 'Nuff said. But WHAT corrosion? My water is high pH (9.0 or so) and a low-middling mineral (carbonate, from limestone) content. That's why they raise the pH, to precipitate out a lot of the minerals. Is anode-rod servicing of importance in this case? What specific properties of water produce the corrosion that anode rods are supposed to deflect? I just got a new water heater, but my old one was going strong after almost 20 years with no anode rod replacement.

Refer to the figure on the first page of this document:

https://nuclearpowertraining.tpub.c...n-The-Corrosion-Rate-Of-Iron-In-Water-117.htm

It shows that the corrosion rate for iron in water is approximately constant from pH 4 to pH 9. If the pH was 14 you wouldn't have to worry about the metal in the tank, so the anode wouldn't be needed. Unfortunately at that point the water would be so extremely basic that it would destroy the glass lining in the tank (eventually), and any bodily tissues that came in contact with it.

So yes, you need to check that anode rod.

 

[pasadena_commut]

There are powered anode rods out there that use a small power supply plugged into the AC line. The advertised 20-year warranty seems attractive even though the initial cost outlay of the device is upwards of $175.

Has anyone tried one of these and, if so, do they really work for ~20 years?

I have never encountered a small plug in power supply that has a service life of 20 years. Not saying one couldn't be built, but if you buy a 5V or 9V power supply from Ebay or Amazon, like the ones used to power a home wifi router, you will probably be replacing it within 5 years.

The powered anode rod is a sound concept, but it is important that there be some sort of warning system so that the user can remedy a fault if the system ever fails, as from a bad power supply, or a broken wire.

 

[Ludington]

This is all fascinating, but water on iron - that's rust. I've always wondered how an anode rod stops it on the tank wall, since water contacts it there regardless (if the coating has cracked)
I must have gotten a good tank, as it's 24 years old, the anode rod is long gone, still runs fine. Might be pulling a little high on the watts 5800 instead of the rated 5500. I'm going to swap it out pretty soon. There easy to change out, but my age and maladies are starting to limit me. Need to get one that's a set it and forget it type... that's a marathon. (I think)