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Old 03-26-2015, 01:56 PM   #1
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can I mount an expansion tank in the crawl space?


I'm getting different answers depending on the source but basically here's the deal.
I need to replace my HW heater which is located in a coat closet. Not much room in there as it is. This house never had an expansion tank so I plan on installing one with this new heater.
Some sources say to install the expansion tank as close to the HW heater as possible, with examples always showing the tank above or in the same location as the heater. Also there is said to be no shutoff device between the expansion tank and heater. Other sources say that operationally, it really doesn't matter as long as its on the cold run somewhere in between the incoming pressure regulator/reducer and the heater.

Space is an issue in this closet and it'll be a game of Tetris to install the expansion tank in the same space as the HW heater.
So I'm wondering if I can install it in the crawl space directly under the floor of the water heater. We're talking 6' down and maybe 3' over from where the tank sits now. It will be on the cold supply but between the regulator and the shutoff valve to the heater; thus violating one of the rules mentioned above.
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Old 03-26-2015, 02:27 PM   #2
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It must be protected from freezing, be accessible and have no valves between the exp tank and wh.
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Old 03-26-2015, 09:47 PM   #3
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If you never had an expansion tank, I would assume you don't have a check valve on your main line coming in to the house. Is there really a need to add the expansion tank in this case? Why do you think it's necessary?
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Old 03-27-2015, 08:15 AM   #4
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Originally Posted by readar View Post
If you never had an expansion tank, I would assume you don't have a check valve on your main line coming in to the house. Is there really a need to add the expansion tank in this case? Why do you think it's necessary?
My question too. None of my homes has ever had an expansion tank associated with the water heater. Why do you think you need one?

Are you on a well? If so, you definitely need an expansion tank, but it really has nothing to do with the water heater. Do you have hot water heat? One of my houses did, and it had a small expansion tank.
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Old 03-27-2015, 10:50 AM   #5
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The standard nowadays is to install an expansion tank just above the water heater where, among other reasons, an inspector for your water heater installation can readily see it.

More and more these days, check valves are installed in the incoming main water line. You might not have a check valve now but the water company might install one during an upcoming water meter inspection.

Each new tankful of water heated expands slightly. In some cases, with a check valve or pressure regulator on the main incoming (cold) water line, and no expansion tank, this has caused frequent trips of the water heater's relief valve.
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Old 03-27-2015, 12:16 PM   #6
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Quote:
Originally Posted by AllanJ View Post
The standard nowadays is to install an expansion tank just above the water heater where, among other reasons, an inspector for your water heater installation can readily see it.

More and more these days, check valves are installed in the incoming main water line. You might not have a check valve now but the water company might install one during an upcoming water meter inspection.

Each new tankful of water heated expands slightly. In some cases, with a check valve or pressure regulator on the main incoming (cold) water line, and no expansion tank, this has caused frequent trips of the water heater's relief valve.
Yes, if the original poster already has a check valve installed in the incoming main water line, thermal expansion without an expansion tank could have manifested itself as:
  1. leaking from the water heater's relief valve.
  2. leaking from faucets.
  3. leaking in the toilet tank's fill valve.
  4. expansion of the washing machine's rubber hoses.

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Old 03-27-2015, 04:33 PM   #7
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I'm not 100% sure there's a check valve but my relief valve burps once in a while, usually after a big drain off the HW heater. It doesn't vent outside either so I have a bucket underneath it to catch the water for now.

I have the water district coming out next week to measure the pressure, I can ask then whether or not there is a check valve. I'm pretty sure there is.
This house was built in the 70's in a sort of "vacation-home" community but has tripled in density with modern builds over the last 10 years, so updates to the water feeds may have been made w/o us older-home owners even knowing.
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Old 03-27-2015, 04:52 PM   #8
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Quote:
Originally Posted by 211 View Post
I'm not 100% sure there's a check valve but my relief valve burps once in a while, usually after a big drain off the HW heater. It doesn't vent outside either so I have a bucket underneath it to catch the water for now.

I have the water district coming out next week to measure the pressure, I can ask then whether or not there is a check valve. I'm pretty sure there is.
This house was built in the 70's in a sort of "vacation-home" community but has tripled in density with modern builds over the last 10 years, so updates to the water feeds may have been made w/o us older-home owners even knowing.
Water heater's relief valve burping after large hot water usage is an indicator that you need a thermal expansion tank.

Even if you learn that there is no city installed check valve, if you have a pressure reducer (pressure regulator) verify that the model number has a built-in bypass valve. If there's no built-in bypass valve in it, then the pressure reducer can act as a check valve. --- And even if there is a bypass valve in your pressure reducer, if the city's water pressure is too high, then there will still not be any back-flow into the city's system to relieve thermal expansion.

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Old 03-27-2015, 05:28 PM   #9
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Okay, so now that we've determined I need an expansion tank... can I mount it in the crawlspace?

sounds like no, but more for visually appeasing whoever comes in to check it rather than anything logically or functionally wrong with the actual location.
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Old 03-27-2015, 06:05 PM   #10
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Yes you can mount a expansion tank anywhere on the cold water from the meter in as long as it will not be exposed to freezing. Don't forget the winter we just had.
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Old 03-27-2015, 06:20 PM   #11
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Quote:
Originally Posted by 211 View Post
Okay, so now that we've determined I need an expansion tank... can I mount it in the crawlspace?

sounds like no, but more for visually appeasing whoever comes in to check it rather than anything logically or functionally wrong with the actual location.
Nothing says it must be at the water heater. If somebody wants to see it they can ask you where it is......
Whereever you put it, dont rely on the pipe to support it. Anchor it to a joist or something. And keep it off the ground too
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Old 03-27-2015, 06:51 PM   #12
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Quote:
Originally Posted by Ghostmaker View Post
Yes you can mount a expansion tank anywhere on the cold water from the meter in as long as it will not be exposed to freezing. Don't forget the winter we just had.
And verify that there isn't a heat trap ball valve in the cold water input to your water heater. That could negate the use of a thermal expansion tank in the cold water line. If there is one, verify how well it seals by checking the water pressure from a cold water faucet during tank water heating.


Image from: http://waterheaterreviews.com/what-is-a-heat-trap

HRG

Last edited by Homerepairguy; 03-27-2015 at 06:54 PM.
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