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Thread: Questions about over flow value and adding a expansion tank

  1. #1
    DIY Junior Member Sammy222's Avatar
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    Default Pressure release valve on water heater and adding a expansion tank

    About 6 months ago they replaced my electric water heater with a 50 gallon Bradford white because the pan was constantly full. Yesterday I noticed about 2 inches of water in the pan. Call the installer of the water heater and they came out and decided it was where the pressure release valve on top of the water heater would release water ever so often. (It's not a constant run out of the pressure release valve, its actually dry on top,but you can see where it has a water stain where it's run off the top and down the side). They placed a PVC pipe off the pressure release valve and down the side, and they installed a expansion tank. This morning looks like the overflow valve released a little and the floor was a little wet/damp. I don't know if a lot of water came out because the plumber placed the end of the pipe outside the pan. Did I need that expansion tank for this electric heater? And does the expansion tank reduce the release of water from the pressure release valve? Should i call them back if i still getting small amounts of released water from the top valve? They had the water heater set on factory settings when they installed and this plumber increased the temp a little. I appreciate anyone's advice, thanks
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    Last edited by Sammy222; 02-03-2013 at 10:04 AM. Reason: Mistakes in post

  2. #2
    Test, Don't Guess! cacher_chick's Avatar
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    There is no such thing as an "overflow" on a water heater. It is a temperature and pressure release valve, and it is there to prevent the water heater from over-pressurizing when something is wrong. No water should ever come out of it unless something is wrong.

    When water is heated, it expands. The expansion tank is meant to give somewhere for this expanding water to go. Something in your system is not working properly and the drainage is a symptom of that problem.

  3. #3
    DIY Junior Member Sammy222's Avatar
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    Did they need to install the expansion tank? Should any water ever come out of the pressure valve? Thank you for your help

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    DIYer, not in the trades LLigetfa's Avatar
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    TPR valves are sort of like airbags. They are not meant to be deployed frequently and repeatedly. If the TPR has been frequently relieving due to expansion pressure, it is now suspect and should be replaced. You might want to put a tattler pressure gauge on your system to see what the peak pressure rises to.

    That expansion tank should be properly supported.

  5. #5
    Test, Don't Guess! cacher_chick's Avatar
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    The expansion tank is required if you have a closed water supply system. It did not have to be installed where they installed it, but that is not the cause of your problem.

    As I stated before, water should never come out of the temperature and pressure relief valve unless something is wrong. If your plumber installed the water heater and expansion valve, he should be held to diagnosing the problem.

  6. #6
    DIY Junior Member Sammy222's Avatar
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    The water heater was installed 6 months ago, he installed the expansion tank yesterday. He said that was the problem, and then he ran the PVC pipe down the side, I guess that's why he ran the pipe outside the pan so I couldn't see if water was collecting.lol I don't know much when it comes to plumbing, so how do you tell if or what is a closed system.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Unless I'm misunderstanding the code, the pipe from the T&P valve cannot be the type of pipe he used. It must be able to withstand extremely hot water and CANNOT have ANY restrictions in diameter. I can't see where yours terminates, but there are rules on that as well.

    That valve is an emergency, safety valve - it should NEVER open on a regular basis. If it does, something's wrong. Where I live, they REQUIRE an expansion tank with any water heater...so, whether you technically need one for mechanical reasons or not, I must have one where I live. Whether you need one or not, it's not a bad thing to have. It must be pumped up (like a tire) before installation to the proper pressure, or it can't do it's job properly.

    Especially if you have hard water, regular opening of the T&P valve may mean that it has built up some mineral deposits, and most good plumbers would replace it. That valve is designed to open if the pressure ever gets too high (the expansion tank should resolve that) OR if the temperature gets to high (almost to boiling - you'd notice if it got that hot!). The idea is, relieve the pressure in the tank so that it can't get to boiling and blow up.

    Since that valve is designed to only open if the pressure exceeds 150# or it gets hotter than 200-degrees, unless you have exceptionally high water pressure in the home, the expansion tank should have solved your problem unless the T&P valve can no longer seal well, there are some deposits on it, or you've worn it out from frequent discharges.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    In the Trades Gary Swart's Avatar
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    I have serious doubts about the qualifications of the installer. No real plumber would install an unsupported expansion tank, and certainly not real plumber would use PVC pipe from the T/P valve. There are a couple of reasons an expansion tank is installed. First, if your local codes require it for all water heaters. This is not true for every location. The other reason for the tank is if you have what is called a "closed system". This occurs when there is a check valve in the water supply that will prevent the water expansion that happens when water heats from being absorbed by the city water main. The most common of these check valves is a pressure regulator valve that regulates the home's water pressure. These have a built-in check valve. As previously explained, the T/P is a safety valve that will trip to relieve excess water heater pressure or temperature. If you have a closed system without an expansion tank, the pressure in the heater will rise very quickly when the water is being heated and it will trip the T/P. If it did not, the heater would become a bomb (literally). I would suggest you contact a licensed plumber to come in and evaluate your situation and rectify the problem. Forget about the installer, he's a hack.

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    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by Gary Swart View Post
    I have serious doubts about the qualifications of the installer. No real plumber would install an unsupported expansion tank, and certainly not real plumber would use PVC pipe from the T/P valve...
    It looks to me to be PEX, not PVC. Still, it looks like shoddy work and I wonder why the installer would not have run it into the pan. Also, doesn't the pan normally have a drain?

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    DIY Junior Member Sammy222's Avatar
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    Quote Originally Posted by LLigetfa View Post
    It looks to me to be PEX, not PVC. Still, it looks like shoddy work and I wonder why the installer would not have run it into the pan. Also, doesn't the pan normally have a drain?
    I'm going to call them back out tomorrow to place some support. Did I really even need the expansion tank? I never had one before And there is a drain in the pan, I guess he just didn't put the pipe in there, and the floor was damp this morning

  11. #11
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by Sammy222 View Post
    Yesterday I noticed about 2 inches of water in the pan.
    Quote Originally Posted by Sammy222 View Post
    ...And there is a drain in the pan...
    If the pan has a drain, why was there 2 inches of water in it?

    If the TPR was popping off, then you most likely needed the expansion tank as Gary mentioned. Just because you got away without one before doesn't mean you don't need one. Perhaps your city water dept installed a backflow preventer recently. Perhaps a toilet or humidifier fill valve used to relieve the excess pressure before.

    With the TPR popping off frequently, it probably built up with hard water scale on the valve and will no longer seat properly. As I said before, they are not designed for repeated opening/closing and can start to leak.

  12. #12
    Retired Defense Industry Engineer jadnashua's Avatar
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    Code does NOT allow pex for a WH T&P outlet...that pipe is only rated to 180-degrees and the fittings have restrictions. That safety valve opens for one of two reasons, and the temperature it will trigger at is 200 (pressure, 150#, which is also beyond the spec for that pipe). That pipe will not be able to keep the tank from potentially exploding, and is likely to fail should it ever really be needed. This obviously was not installed with a building permit or an inspection, if it would have failed.

    Again, the T&P opens for one of two safety, emergency related situations: pressure that exceeds 150#, or water temperature above 200-degrees. Now, lots of things could cause it to not re-seal, once opened, and once opened like yours has, it should be replaced.

    IF you have a closed system, the pressure increase (unless there's a leak somewhere) can EASILY get high enough to open the T&P valve when there isn't an expansion tank, or if the expansion tank has failed. Tap on yours, if it rings like a bell, it's probably okay (other than needed to be supported - when they fail, it will fill up with water an be quite heavy...you need to support it for when that happens sometime down the road). If it thuds, like it's full of water, it probably is, and is probably defective.

    I can't tell for sure, but the expansion tank MUST be installed on the cold inlet side of the WH, not on the hot, output side. It is supposed to be installed between the tank and any shutoff, so it will always be there (the valve would isolate it from the tank).
    Last edited by jadnashua; 02-03-2013 at 01:56 PM.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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