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Thread: Replacing T/P Relief valve using PVC instead of copper?

  1. #1

    Default Replacing T/P Relief valve using PVC instead of copper?

    I've seen my basic problem (hot water disharge from the T/P relief valve) previously discussed in this forum. Thanks to all for your input. I checked the water pressure (about 60 psi), and I don't have a PRV or expansion tank. Now I think I am ready to try replacing the T/P valve. My next question is can I replace the copper discharge pipe that runs to the outside of the house with PVC? After I replace the T/P valve, I'd like to install the drain line with a connection that I can attach and detach without soldering, if that is acceptable. Any comments?

    Thanks!

  2. #2
    Plumber jimbo's Avatar
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    You can't use any PVC inside the house, and specifically never on water over 70. You can use CPVC, but it is not recommended to connect that directly to the water heater.....you need about 18" of copper to keep the high heat off the plastic.

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    Plumber BAPlumber's Avatar
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    what is the temp. of the hot water? this could be why the t&p is opening.

    Brent

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    Plumber BAPlumber's Avatar
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    It'll be okay to connect 3/4 CPVC to your new tp valve. CPVC is rated at 100 psi at 180 F, and since this is an open drain line there is virtually no pressure on it. Also, the tp should be opening before 180F anyway.

    Brent

  5. #5

    Default Replacing T/P, using PVC?

    Quote Originally Posted by jimbo
    You can't use any PVC inside the house, and specifically never on water over 70. You can use CPVC, but it is not recommended to connect that directly to the water heater.....you need about 18" of copper to keep the high heat off the plastic.
    Thanks for the info. I got the idea that using PVC was OK based on another thread and a photo (Sorry, I don't know how to link to it or quote it, but it is pasted below). This is a gas water heater in an indoor laundry room. I have to cut off the old copper drain pipe to get out the old T/P valve because it goes straight down, then a 90 along the floor and outside through a hole in the wall, then another 90 elbow to the ground. Should I just get someone to sweat it back on using a new fitting into the new T/P valve? I thought putting in some kind of threaded connection would make it easier in the future. I guess I could achieve both objectives by sweating on at least 18" of copper, then putting in a connection to PVC (or CPVC?). Is that a good idea, or more trouble than it is worth?

    As far as the other reply asking about the temperature, I'll have to check it. I don't think it is excessive, and I've kept the thermostat on low, but I haven't measured it yet.

    Thanks again, and in advance for any advice. As you can tell, I'm a novice, but fairly intelligent and cautious, I think. I'll call in a professional at the first sign of trouble, or if replacing the T/P valve doesn't stop the excessive discharge. The T/P valve is missing the handle, so I think it should be replaced regardless of the drainage.

    Lisa


    The other thread that had the photo using PVC:
    "07-04-2007, 11:58 AM
    daddyslipdisk
    Junior Member Join Date: Jul 2007
    Posts: 4

    Replaced Pressure valve

    Ok, Well I did a few things to try and remedy this problem. the first thing I did was replace the pressure valve. I also purchased a long PVC drain pipe that I attached to the pressure valve so that it just goes straight down to the floor and into a bucket instead of the long winding path it took before. My neighbor who is an HVAC guy for Coolray said that would be fine, but that it wouldn't pass inspection. He said that I would either need to have drainage put in there somehow or get the expansion tank. But he said for now my issue should be resolved and everything should be fine.

    I turned the gas back on, lit the pilot and then turned the water back on. So far, there are no leaks at the pressure valve and no drainage coming out of the PVC pipe into the bucket. Actually, I just checked and there were like 2 drops in the bucket.

    I figure that if I use the pressure switch each month, that should quell any concerns about pressure build up. Any thoughts? The new repairs are at [U]www.hortonwebdesign.com/heaterfix.htm and the old, bad configuration is at www.hortonwebdesign.com/heater.htm. I just want to make sure that I haven't made a ticking water heater bomb that will endanger my family."

  6. #6
    Master Plumber master plumber mark's Avatar
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    Talking cpvc or pvc??

    I see sooo many people useing pvc sch 40
    for both hot and cold water lines in their homes...

    The cpvc is what is supposed to be used for pressurised water systems.......


    Although personally I cant really see a problem with
    running pvc sch 40 for a straight down to the floor
    pop off valve...it being only a drain line that gets used once in a blue moon anyway...



    are they worried its going to snap off at the
    threaded valve?? sag,
    or melt from the heat??

  7. #7
    In the Trades Gary Swart's Avatar
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    This is about the only place I would suggest using galvanized pipe. It will rarely, if ever, be used so rust and corrosion will never be a problem. It is against code to use PVC, but for the same reasons as noted for galvanized pipe, PVC would work just fine as long as it wasn't caught by an inspector.

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    Jack of all trades frenchie's Avatar
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    Maybe I'm missing something, but... considering that there's a drain line there already... isn't the simplest thing, to re-use the existing? One sweat joint, versus removing the drain line & putting together a whole new drain line. Isn't this a no-brainer?


    La Duena - sweating is about a tenth as hard as you think it is. Especially in this case: since it will never be under pressure, it doesn't even need to be that good a job. This thread:

    http://www.terrylove.com/forums/showthread.php?t=14183

    has all the basics. No need to hire someone, this is something you can definitely do yourself.

  9. #9
    Licensed Grump GrumpyPlumber's Avatar
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    Quote Originally Posted by BAPlumber
    It'll be okay to connect 3/4 CPVC to your new tp valve. CPVC is rated at 100 psi at 180 F, and since this is an open drain line there is virtually no pressure on it. Also, the tp should be opening before 180F anyway.

    Brent
    I think you mistook the 180F for 180psi.
    T&P valves are set at 210F and 150PSI
    Apparently some states allow CPVC off the T&P...here we can't use any plastic for at least 24" linear from any heater or boiler.
    .
    "The biggest regrets we have in life are the chances we never took."

  10. #10
    Plumber BAPlumber's Avatar
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    Quote Originally Posted by GrumpyPlumber
    I think you mistook the 180F for 180psi.
    T&P valves are set at 210F and 150PSI
    Apparently some states allow CPVC off the T&P...here we can't use any plastic for at least 24" linear from any heater or boiler.
    .
    you're right I made a mistake. In Washington and Oregon I've never been called on the CPVC right off the T&P. both are under the UPC.

    Brent

  11. #11
    Moderator & Master Plumber hj's Avatar
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    Default drain

    In this area the relief drain MUST be 3/4" rigid copper, (no soft copper or flex connectors), because the line has to be a full 3/4" i.d., which CPVC and all plastics are not.

  12. #12
    Licensed Grump GrumpyPlumber's Avatar
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    Quote Originally Posted by BAPlumber
    you're right I made a mistake. In Washington and Oregon I've never been called on the CPVC right off the T&P. both are under the UPC.

    Brent
    I know...my states a pain in da butt.
    "The biggest regrets we have in life are the chances we never took."

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