On Tuesday, February 16, 2016 at 7:06:58 PM UTC-5, Don Y wrote:
On 2/16/2016 4:28 PM, SeaNymph wrote:
I apologize if this was discussed before my time.

We have an 85 gallon Marathon water heater, which I really like. I've read
different things about periodically training water heaters and I don't know
what to believe.

I'm not sure if its necessary, just wondering what others think.

How "hard" is your domestic water supply?

The "textbook" recommendations include:
- replacing the sacrificial anode (it "corrodes", bt design)
- draining the tank (mineral accumulations)
- "testing" the high temperature/pressure relief valve

But, almost all of these can find folks with associated
horror stories.

It's not possible to replace the anode in ours with a "stock"
anode (no clearance above the tank to withdraw and insert).
[though I think someone makes a "hinged" anode for this reason]

If the drain valve breaks (some are plastic!) or refuses to
reseal properly (drip, drip, drip), you're faced with replacing
it. You may not be able to find a suitable replacement
(many tanks are glass lined; metal into glass is a big FAIL)

Likewise, testing the TPR valve can leave you with a valve that
no longer closes. In addition to depriving you of future
hot water, you may also end up with *no* water (if there is
not a shutoff on the intake and outtake of the water heater
so you can isolate it from the COLD water supply!)

Bottom line: don't do any of these the day before you have
house guests scheduled to arrive!

+1

If you're planning on periodically draining it, I'd replace the
cheap drain valve with a quality one at time of installation.

Anode replacement, not sure what to do. One theory is that
checking and replacing it will prolong the life of the tank.
The other is that the anode is good for the life of the tank,
and even if you do replace it, it won't do much to extend the
life of the tank, because it's going to fail anyway from other
causes. Probably depends a lot on the water you actually have
too.