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Old 10-30-2012, 09:01 AM   #1
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Two plumbing questions: Water heater drain and expansion tank.


I have a couple questions about water heaters.
The first one is a purely practical question. I need to replace my 11 year old electric water heater and the builder-installed one was installed in an internal closet directly on hardwood floors with no drain pan.
A recent leak in my garage installed second water heater has spooked me and I want to install a drain pan. The problem is there really is no practical way of getting a drain pipe to the outside. There is a relatively straightforward run through drywall to a shower cubicle in my second bathroom.
Would it be acceptable to run PVC from the drain pan to a (say) chrome short pipe just protruding through the cultured marble of the shower cubicle?
I'm pretty sure I can make the outlet look presentable enough; any thoughts?

The second question is less practical, more theoretical. I understand the function of the expansion tank near the water heater: Basically, when there is a check valve or PRV in your cold incoming supply the system is closed in that expansion in the heating water in the tank has nowhere to go. But surely in most systems (as in my house) even just one toilet cistern would satisfy this need since the cold water supply can now expand into the air space in the cistern. What am I missing?

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Old 10-30-2012, 10:25 AM   #2
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Two plumbing questions: Water heater drain and expansion tank.


You could install an auto shut-off in the pan. If it senses water, it will turn off the water supply. I put a wags valve under my gas heater, I'm sure they would have one to cut off the water and electric.

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Old 10-30-2012, 10:50 AM   #3
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Two plumbing questions: Water heater drain and expansion tank.


I do not believe that would be acceptable. Could you imagine if someone was in the shower when the valve let go. Scalding hot water would be sprayed all over them.
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Old 10-30-2012, 10:57 AM   #4
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Two plumbing questions: Water heater drain and expansion tank.


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I do not believe that would be acceptable. Could you imagine if someone was in the shower when the valve let go. Scalding hot water would be sprayed all over them.
Wow! I had no idea such a thing was available. That sounds like a great idea. Regarding the scalding hot water shower - this wouldn't happen since the valve cuts of the cold supply top the water heater so the person would get a COLD shower not a hot one. Not wonderful but certainly not dangerous.
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Old 10-30-2012, 11:01 AM   #5
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Two plumbing questions: Water heater drain and expansion tank.


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You could install an auto shut-off in the pan. If it senses water, it will turn off the water supply. I put a wags valve under my gas heater, I'm sure they would have one to cut off the water and electric.
One thought: How long do these WAGS devices remain viable for? The warranty is 1 year, of course, but does the fiber degrade over time and render it useless? Will it "fail safe" - i.e. if it does fail, is the failure mechanism one that would shut off the water rather than fail to shut it off in the event of a leak?
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Old 10-30-2012, 11:36 AM   #6
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Two plumbing questions: Water heater drain and expansion tank.


Good question but I'm sorry, I do not know if they degrade over time.
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Old 10-30-2012, 11:57 AM   #7
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Two plumbing questions: Water heater drain and expansion tank.


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Wow! I had no idea such a thing was available. That sounds like a great idea. Regarding the scalding hot water shower - this wouldn't happen since the valve cuts of the cold supply top the water heater so the person would get a COLD shower not a hot one. Not wonderful but certainly not dangerous.
I was referring to your plan to run the overflow from the tank into the shower cubicle.

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There is a relatively straightforward run through drywall to a shower cubicle in my second bathroom.
Would it be acceptable to run PVC from the drain pan to a (say) chrome short pipe just protruding through the cultured marble of the shower cubicle?
I'm pretty sure I can make the outlet look presentable enough; any thoughts?
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Old 10-30-2012, 12:25 PM   #8
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Two plumbing questions: Water heater drain and expansion tank.


What's underneath the water heater? Basement? Crawl space?
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Old 10-30-2012, 12:47 PM   #9
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What's underneath the water heater? Basement? Crawl space?
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Old 10-30-2012, 01:10 PM   #10
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Two plumbing questions: Water heater drain and expansion tank.


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Basically, when there is a check valve or PRV in your cold incoming supply the system is closed in that expansion in the heating water in the tank has nowhere to go. But surely in most systems (as in my house) even just one toilet cistern would satisfy this need since the cold water supply can now expand into the air space in the cistern. What am I missing?
The cold water supply will not expand into the air space in the toilet cistern. The ball/float valve assembly shuts off the cold water supply like a closed faucet does when the level in the cistern reaches "the full mark". So the cistern does not satisfy the need for an expansion tank.

Now if you had a well and water pump, that system will include a pressure tank. This tank will serve the role of a water heater expansion tank provided that any valves in between remain open. An inspector will be happier if he can see the expansion tank while standing in front of the water heater thus a separate small expansion tank above the water heater is best.
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Old 10-30-2012, 02:35 PM   #11
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Two plumbing questions: Water heater drain and expansion tank.


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The cold water supply will not expand into the air space in the toilet cistern. The ball/float valve assembly shuts off the cold water supply like a closed faucet does when the level in the cistern reaches "the full mark". So the cistern does not satisfy the need for an expansion tank.

Now if you had a well and water pump, that system will include a pressure tank. This tank will serve the role of a water heater expansion tank provided that any valves in between remain open. An inspector will be happier if he can see the expansion tank while standing in front of the water heater thus a separate small expansion tank above the water heater is best.
Excellent answer! I knew I must be missing something - it's obvious when you state it like that! As a slight extension to this, I have two water heaters in the two halves of the house (the house isn't really that big, even though I am in Texas!). The one in the garage has an expansion tank, the one inside does not. I presume the one tank for the two heaters is OK?

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