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Thread: Replacing Thermal Expansion Tank

  1. #1
    DIY Junior Member waxgroove's Avatar
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    Default Replacing Thermal Expansion Tank

    Is it difficult to replace a thermal expansion tank?

    I have some "spitting" at the kitchen faucet and when using hot water get some pipe noises - I'm thinking that it might be the thermal expansion tank - air in lines?

    I have a PRV (new) before the 40 gal gas HW - it is set to 60psi. The tank is installed on the cold side after the PRV. I haven't checked the pressure in the tank.

    I try some plumbing things but pressure sort of scares the hell out of me. What all needs to be done to pull this off safely. Steps would be great.

    Thanks

  2. #2
    In the Trades Gary Swart's Avatar
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    Replacing the tank is easy, just screw the old one off and screw the new one on. Best to turn the water off first, and you do have to set the pressure to match the PRV. I'm not sure the cause of you problem is tank failure, but the pressure needs to be checked and set if necessary. You do this with a hand pump like used for bicycles and an ordinary tire pressure gauge. You can check the tank's condition by removing it and seeing if the tank is full of water. Should I point out that if the tank has failed is is full of water, it will be fairly heavy? You should also have a pressure gauge with adapters that can be screwed onto a water faucet to check the PRV pressure. These are available at any hardware store for under $15. I actually permanently plumbed one into my supply line so I can check the pressure at anytime with just a glance.

  3. #3
    Master Plumber nhmaster's Avatar
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    I doubt the tank is your problem.

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    DIY Junior Member waxgroove's Avatar
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    Default Update - tank filled with water

    The expansion tank was filled with water - check pressure and water came out.

    Tank replaced (set to house pressure of 60psi) - but noticed T&P from water heater had started to drip. Could have been from failed tank? I have to watch this.

    I'm getting some "tapping" noises when the hot water is turned on - on the second floor bath. Goes away after about a minute. Could this be still to much pressure in the lines? Is there a way to check pressure on water heater?

    Thanks

  5. #5
    Forum Admin, Expert Plumber Terry's Avatar
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    Default

    I'm getting some "tapping" noises when the hot water is turned on - on the second floor bath. Goes away after about a minute.
    Tapping noises that take a minute to go away, are normally plastic waste lines that get longer and then shorter as they warm and cool.
    As they move against wood, or perhaps tight clamps, they get pretty annoying.

  6. #6
    DIY Junior Member waxgroove's Avatar
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    Default Plastic?

    Thanks for the reply Terry - this forum is very helpful.

    I would like to point out that the slight tapping happens with the faucets and or tub/shower hot water. It sounds like its coming from in the walls, (near the bath) but with noises who knows. These are copper pipes.

    It appears that the plastic pipes for these baths are directed into the attic. I've recreated the noises and went up there to look - nothing. Coming from the walls. There could be plastic pipe in there - I don't know.

    I'm guessing since my previous expansion tank failed - that would have caused the T&P to start acting up. If it continues then I would assume the T&P is bad - I have a 10 year 40 gal GHWH - Bradford White.

    The temperature here today is about 50 degrees - it wouldn't appear to be an expansion thing. What gives?

    I hate plumbing.
    Last edited by waxgroove; 02-10-2009 at 01:38 PM.

  7. #7
    Retired Defense Industry Engineer jadnashua's Avatar
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    A T&P valve can get weak and the shaft coated with mineral deposits and make it hard to seal properly once tripper. But, if yours does seal, you should be fine. If not, replace it.

    The drain pipes are what Terry was talking about...they expand and contract a lot when you run hot water through them. It can be annoying, but unless you tear the walls apart and release the part where it is tight, you'll hear them rubbing as they expand and contract.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  8. #8
    DIY Junior Member waxgroove's Avatar
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    Default OK - I'm listening

    I haven't touched the T&P - I'm confident previous owners didn't check it either - but who knows.

    I ran some hot water at the kitchen sink and the T&P released a little. When using no hot water it remains dry. Is it normal for the T&P to release only when hot water is used? Is this an indication that it should be replaced?

    As for the pipes - is there a way to know (by sound) if the noises are from a copper pipe or plastic? Are we saying that copper doen't expand like the plastic does - i.e that's why the noise goes away after about a minute or so? If it is the copper pipes how much of this can they take?

    Thanks for your help
    Last edited by waxgroove; 02-10-2009 at 06:10 PM.

  9. #9
    DIY Junior Member gabby's Avatar
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    Hey thanks. I may pick me up a pressure gauge. That would be great to check the pressure at anytime.
    Again, thanks for all the help.

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