Water Heater Maintenance

"Winston" (clip) When I pulled the anode, I found that it was coated with calcium and other stuff thoughtfully supplied by our water Co.(clip) ^^^^^^^^^^^^ Something I have never done. Where is the anode located, or how can I recognize it?

Older style water heaters have it located independently of anything else. Look behind the exhaust stack. It's threaded into the top: It looks like the head of a hex bolt, measuring 1-1/16" across the flats.
Newer style heaters have it sneakily hidden under the 'hot water out' pipe. You disconnect the output pipe and unscrew the nip to which it was connected, out of the tank. The anode is attached to the bottom side.
If the tank hasn't been serviced recently, ion migration has caused the threads of the anode and those of the top of the tank to 'become one'. After you shut off the water and gas or electricity to the tank, you may have to spray under the head with penetrating oil and stack ice cubes in an open can over the anode head to shrink the parts away from each other before wrenching it loose. This will require a breaker bar or really long 1/2" drive ratchet.
If the tank is not firmly strapped to the wall, you will need to come up with some sort of strap wrench to hold the top of the tank so you can deal with Newton's Third Law when wrenching.
Beware of newer model replacement anodes. They have a series resistor build in. (I have a bad feeling about series resistors in this exceptionally low-resistance application).
--Winston

The thing you have really to worry about more is that calcium on the anode. The big failure that I've seen with tanks is not the anode going but rather the calcium insulating the tank allowing the wall to develop hot spots where the water boils and erodes the wall.
-- Why isn't there an Ozone Hole at the NORTH Pole?

So I *wasn't* hallucinating.
During a water emergency last year, I connected our temporary water supply "cough" um. backwards, which drove cold water into the 'hot' side of the water heater. Clue: why is hot water coming out of the 'cold' tap? Oh. Swap the supply into the 'cold' side and all is well.
For several days after this particular maneuver, the water coming out of the 'hot' tap seemed to be somewhat hotter than normal. Guess the thermal shock popped off some of that mineral 'insulation' from the inside of the tank and efficiency went up a bit, for a while.
I will be darned. Thanks!
--Winston

Might find the rod is very short - e.g. used up. Buy another at Sears or such. Martin

(Replacing water heater anodes)
The Sears (U.S. department store) in my area doesn't carry them. One needs to visit a real-life commercial plumbing supply store. Be prepared to specify 'aluminum' or 'magnesium'. Consider bringing along your existing anode for comparison. Anodes with a 'bump' in the top of the hex head are magnesium. Without the bump, it may be magnesium or aluminum. Some later model anodes are an alloy of several non-ferrous metals.
--Winston

Hum - Used to and I have replaced an old one with a Sears big one. Times change I suppose - now Sears Holding Company over KMART and Sears. Wonder about Simson-Sears - same way or long gone ? Canada ??!
Martin