"bd" wrote in message
roups.com...

replying to trader4, bd wrote:
And the valve could eventually fail
I looked at expansion tanks today, and in the instructions it plainly states
that the tank WILL eventually fail. Given that both of my hot water heaters
are inside my home and in places where a flood of water would be destructive
and potentially VERY expensive, I think that I could dump a little water
every
now and then.
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for full context, visit
http://www.homeownershub.com/mainten...ve-205964-.htm

First of all; all things can fail some time. Regarding Expansion tank vs
Relief valve
You should have both. However you are need to know what is your maximum
water
pressure supply and "do you have water regulator on the input" (Coldwater
side)
The Relief valve should have adjustment at least 20% higher then you water
supply
The tank recommended size it should be to take 5-10% of your water heater
capacity
Thank should be one that have balloon in it "not just open tank", open tank
require
bleeding while one with balloon can be adjusted by adding some air into it
or let out.
However I do not see the need, because Expansion tank would not be any help
on Hot
water heater, Expansion tanks are use on; close loop systems like hot water
heating systems.
On the hot water heaters for washing and bathing would be useless.
The best you can do, in your situation is have made the pan that fits under
the heater
with the drain to dispose of water if leak occurs, in case heater is to open
leak.