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Thread: Water Heater Relief Valve

  1. #1
    Junior Member TUL's Avatar
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    Default Water Heater Relief Valve

    I have a water heater in a finished basement the does the pressure relief valve have to piped outside or can it be piped down to the pan? Venting it outside will require cutting alot of sheetrock because it is located in the middle of the house. Any help will be appreciated

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    Illinois Licensed Plumber SewerRatz's Avatar
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    Here is the code in Illinois about what you asked. Illinois has one of the stricter codes, so I say its best to ask your city plumbing inspector what your requirements are.

    d)Relief Discharge Outlet.



    1) A relief discharge outlet shall be indirectly connected to waste. The discharge pipe from the relief valve shall not be located so as to create a safety hazard or to discharge in such a way as to cause damage to the building or its contents. The relief valve shall not discharge through a wall into the outside atmosphere or where there is a possibility of freezing.



    2) No reduced coupling, valve or any other restriction shall be installed in the discharge line of any relief valve that would impede the flow of discharge. The discharge line shall be installed from the relief valve to within 6 inches of the floor or receptor and the end of such line shall not be threaded.



    3) Any piping used for discharge from the relief valve shall be of metallic material and conform with the requirements of Appendix A, Table A (Approved Materials for Water Distribution Pipe) for potable water piping and shall drain continuously downward to the outlet.



    4) The discharge piping shall discharge indirectly into a floor drain, hub drain, service sink, sump or a trapped and vented P-trap which is located in the same room as the water heater. (See Sections 890.1010 and 890.1050(a), (b) and (c).) The trap must have a deep seal to protect against evaporation or shall be fed by means of a priming device designed and installed for that purpose. (The use of a light grade oil in the trap will retard evaporation.)

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    Moderator & Master Plumber hj's Avatar
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    Default discharge

    If the relief valve opens for anything than an occassional thermal expansion problem, the pan will overflow almost instantly, so that is not even an option to consider. And it CANNOT go up and overhead to a safe location.

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    Plumber Cass's Avatar
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    Most jurisdictions will not allow it to discharge into the pan unless the heater is above the flood rim of the pan because a slow continuous unnoticed discharged from the T&P will rust out the bottom of the heater...where I am if the floor drain is located more that a couple of feet from the pan we install a 1" T on its back in the pan drain line about 8" from the pan and go up 3" to a 1.5" X 3" coupling bushed down to 1" then we run the T&P over to it. This is what the inspectors want here...


    T&P Valve looking at two sides.
    Last edited by Terry; 04-24-2009 at 10:22 AM.

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    Plumber jimbo's Avatar
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    Quote Originally Posted by TUL View Post
    I have a water heater in a finished basement the does the pressure relief valve have to piped outside or can it be piped down to the pan? Venting it outside will require cutting alot of sheetrock because it is located in the middle of the house. Any help will be appreciated
    The biggest problem with your basement location is that the discharge line must slope continuously DOWN from the heater. Any upward-sloping pipe would allow condensation or drips to settle back at the valve seat area, causing corrosion/buildup.

    So you will need a floor drain or sump. Find out what is typically done in your area.

  6. #6

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    Quote Originally Posted by jimbo View Post
    The biggest problem with your basement location is that the discharge line must slope continuously DOWN from the heater. Any upward-sloping pipe would allow condensation or drips to settle back at the valve seat area, causing corrosion/buildup.

    So you will need a floor drain or sump. Find out what is typically done in your area.

    No floor drains or sump in my basement. I only have a bucket placed under the TP pipe.

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    Remodel Contractor GabeS's Avatar
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    Also, make sure there are no shutoff valves between the PRV and the outlet.

    I took a home inpection course and you'd be surprised of all the stuff they showed us. People have done the craziest things to their houses. Most of the stuff was dangerous but sometimes I couldn't help but laugh.
    Gabe

    Don't follow my advice, I only know a thing or two about a thing or two.

  8. #8
    In the Trades Gary Swart's Avatar
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    If you do not have a drain in the basement, you probably should have a plumber on site determine just how or even if you can provide a legal drain for the TP. This is NOT a PRV, by the way. The TP is a safety valve that releases if the temperature or pressure gets too high. A PRV is a pressure regulator valve that reduces your water supply pressure if it is too high and you don't even need one if your supply pressure is not excessive. A TP is absolutely required on all water heaters to keep the tank from exploding in case of malfunction...and yes Virginia, they darn well can explode big time! A tripped TP is not dangerous, but it can certainly cause a problem if undetected.

  9. #9
    Radon Contractor and Water Treatment 99k's Avatar
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    I just don't see an issue with a TNP valve in a finished basement. I have never had a TNP valve leak ... ever. You have much more risk of the tank eventually getting a pin hole and causing a wet floor ... that eventually will happen with any water heater. If you are nervous, keep the HW heater in a pan, plumb the TNP to the pan (6" away), and install a "burst buster" electronic ball valve with a sensor in this pan. If the sensor senses water, the electronic ball valve will close, and the pressure to the tank is removed ... you will immediately know there is a problem by loss of water pressure.

  10. #10
    Retired Defense Industry Engineer jadnashua's Avatar
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    Taco's WAGS valve, is totally mechanical...no electicity required to shut off the water supply if there's a leak and, it can be often wired to disable the gas valve, preventing the WH from turning on with an empty tank. www.wagsvalve.com. It uses a disolvable pellet that releases a spring loaded valve...the same pellet thing that is used on life vests for airplanes when they get wet.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  11. #11
    Master Plumber Redwood's Avatar
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    Quote Originally Posted by jadnashua View Post
    Taco's WAGS valve, is totally mechanical...no electicity required to shut off the water supply if there's a leak and, it can be often wired to disable the gas valve, preventing the WH from turning on with an empty tank. www.wagsvalve.com. It uses a disolvable pellet that releases a spring loaded valve...the same pellet thing that is used on life vests for airplanes when they get wet.
    Yep! But they are a one shot deal.

    The electronic valve with the sensing module is multi shot!

  12. #12

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    Quote Originally Posted by jadnashua View Post
    Taco's WAGS valve, is totally mechanical...no electicity required to shut off the water supply if there's a leak and, it can be often wired to disable the gas valve, preventing the WH from turning on with an empty tank. www.wagsvalve.com. It uses a disolvable pellet that releases a spring loaded valve...the same pellet thing that is used on life vests for airplanes when they get wet.


    I have been thinking of adding something like that to my tankless.

    On Thankgiving morning I took a shower. After the shower, I kept hearing this noise in the water pipes like a valve was just barely turning on. Kind of a higher pitch whining noise. Checked all the fixtures in the house, but I still heard the noise.

    Went downstairs to check the laundry area, and then I find the tankless running with no demand. There was HOT water coming out the T&P valve, and the tankless kept on heating the water. I shut off the gas and let things cool down.

    The next day I went though the heater. Checked water valve and thermostat. It turns out that the T&P valve just started to leak near the thermostat setting. After the hot water demand was turned off, the water temperature at the T&P rose just enough to make the T&P valve leak. Then the point was hit where the burner came back on. So the unit was acting like there was hot water demand, but it was only a defective T&P.

    Good thing I noticed the noise before I left the house for the day!

  13. #13
    Retired Defense Industry Engineer jadnashua's Avatar
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    How often you you expect a WH to leak? It leaks, you replace it, you replace the valve. What do you do if the power is off and your fancy electronic control can't work? Not a problem with the WAGS valve.
    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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