Our Water Heater Anode Experiment
Awhile back we were pondering anode rods in water heater tanks. See, the anode rod is what keeps the tank from corroding and developing a hole which pretty much renders the water heater useless. There is a very big water heater company that doesn't make the anode rod accessible as an easy change out. They make it part of the hot water outlet nipple. This means its going to be difficult to remove and probably no one will bother. That way they sell more water heaters by building in this decay factor. They know pretty well how long the anode will last so they warranty the water heater for that amount of time. When I asked them why they made it hard to change the anode rod, they replied ''why would you want to do that''! Guess as a plumber I'm supposed to look at water heater replacements as a good thing, but I'd rather do the maintenance on them and see them last for decades.
That got us thinking. I studied old literature on anode rods and was intrigued by a nagging question. Does the anode rod have to be in the tank to protect the tank? No one seemed to be able or be willing to answer this. The water heater companies sure weren't going to answer it. Its not in their interest to make water heaters last longer. I recalled my Navy days when one of my duties was to replace the anodes on submarines. Every year we would drydock the sub and crawl into the ballast tanks and replace about a thousand zinc anodes that had pretty well rotted away as they protected the steel hull. This made me think, that the anodes way up front in the ballast tanks seemed to still protect the area way back aft by the rudder. My studies told me that the anode had to be in the electrolite (water) and be in contact electrically with the metal to be protected. Picture in your mind a little you running down the anode rod, then diving in the water, can you swim thru the tank and then run along the metal pipe back to where you started? If so you have met the criteria of being in the electrolite (water) and being in electrical contact with the metal your trying to protect. Electrical contact, continuity, not a direct physical contact. So since no one would tell me if it would work or not to move the anode rod outside the tank and into the piping we figured we had best conduct our own experiment.
My water heater was about 14 years old but very well maintained. I've changed my anode rods several times over the years. So what I did was to pull and cap off the anode port in the tank, and install a brand new anode rod in a chamber that was built in the cold water feed pipe. I've been monitoring this experiment for the last year. So far, so good. The anode rod is decaying just as it is supposed to. Hopefully that means its still protecting the tank. Time will tell. Since a water heater company will void the warranty if the anode rod is removed, they must therefore figure it won't last 5 years. So if my tank lasts 5 years longer with the anode rod moved to an exterior chamber I think I will feel confident that its still protecting the tank. Its now been one year as of May 09.
Below are links to the documentation I've been doing on this experiment. I'll keep adding to it as the experiment makes progress.
Conclusion- today the 20th of July 2014, the tank ruptured and had to be replaced. So here is what I learned.
A little over twenty years ago I replaced a bunch of water heaters on my block. About five or six years ago, all except mine were replaced. I was doing my anode maintenance. Either I got the best water heater of the bunch, or doing maintenance really helped. You decide. In retrospect I don't know if the monetary expenditure for all the anodes rods and the time involved would make it worth while. Hope this information is of some use to someone.
Above is a picture of the core wire that is left after the anode rod pictured on the right side in its ''new'' state is depleted 100 %.