David Starr wrote:
I've got a 4 year old 40 gallon gas water heater. Every now & then,
the T&P valve opens and 3 or 4 gallons drain out. The temp isn't set
too high - 1 on a 1-3 scale - so I don't think it's getting too hot.
It seems to happen when I'm using a fair amount of hot water for a
long period of time.. I have a home darkroom & sometimes need water
at 75 degrees for a couple hours; this is when I notice it happening.

Would it be a good idea to replace the T&P valve, or what? Do these
valves deteriorate over time? The valve appears to be doing what it's
supposed to, but I can't figure out why it's happening. Our previous
water heater never did this.




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Dave Starr, Senior Shop Rat Emeritus: 14,647 days in a GM plant.
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I was not going to reply since Jim and Jeff covered the answer very
well, but I have to congratulate you for giving such a accurate and complete
description including observations few people would notice. You made it
easy to identify the problem. Expansion tank it is. (defective or none
existent)

--
Joseph Meehan

26 + 6 = 1 It's Irish Math