Water heater leak

Or, be careful what you ask for. :-) Just closed on a house. While suffering in an apartment, I kept telling people "I love to fix stuff - I can't wait!" Voila.
Won't be ready to move in for a week, but I had to move a few things in last night, just to be ceremonious. A coffee cup, fishing pole. Anyway, I went down in the cellar and noticed a small puddle of water beneath the overflow tube of the water heater. The thing's still under warranty, so I'm not worried. But, I'd still like some insight as to what that tube's purpose is, and what might fail on a 6 month old unit. The tube's white plastic and leads from the top of the heater down the side. It's a G.E. -Doug
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Doug Kanter wrote:

Dischg from the relief valve tube does *not* indicate heater failure. It will dischg water if the temp is too high (read:scalding) OR, more likely, if the pressure goes too high (over 150 PSI).
This is a *very* common problem most often caused by thermal expansion of the water when heated. Of course, it could be a defective relief valve, but that's not so likely on a 6 mo old unit.
The fix includes adding a thermal expansion tank (assuming I'm right). Much more info here: http://www.flexconind.com/html/wh-series_.html
Easily do-able by a guy who likes to fix stuff...
Jim
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suffering
wait!"
last
went
overflow
is,
I have so many apps running that if I start the browser, this machine will crash. Couldn't a thermal expansion tank be what we tech types call a bowl? :-)
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Doug Kanter wrote:

Bowl??? Not likely..You must be thinkin' crappers. <G>
Expansion tanks become required when your water meter installation and/or an auxillary pressure reducing valve acts like a check valve and won't let pressures equalize by allowing water to move backwards from the house piping to the supply. Check valves may be mandatory some places to prevent polluting the town water system with stuff growing inside your home's plumbing.
Heating cold water makes it expand, and since the heater tank and plumbing system is essentially a rigid walled fixed volume container (until someone opens a faucet), if there's a check valve in use the system pressure will rise quickly when the water expands. That's probably what's causing your water heater's "T&P" valsve to open to relieve that presure.
An expansion tank, in its simplest form, is just a closed tank with a pipe coming from its bottom which connects to the home's plumbing system. The "air pocket" above the water in that tank /is/ compressable and changes volume to accomadate the temperature induced expansion and contraction of the water in the plumbing system.
Those tanks usually have a "tire valve" fitting on top of them through which you can squirt some air with a bicycle pump to "balance" the system and maximize its capability.
Simple tanks like that suffer from the compressed air getting absorbed in the water over time, neccessitating pumping more air into them periodically. More sophisticated expansion tanks use a flexible rubber diaphragm at the water/air interface, which avoids the just mentioned air absorption problem for many years. (Until the diaphragnm develops a leak.)
Recently some innovative designs for expansion tanks have evolved, including tall skinny ones which can be installed in the normally wasted "corner space" between a round water heater and a square closet.
HTH,
Jeff
--
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
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Try turning down the temp first
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