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  1. #1
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    Default tpr drain to trap

    Is this setup kosher? The TPR drain is on the right, 3/4" copper, the 1/2" pipe on the left comes from the trap primer at the top of the photo.

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  2. #2
    Richard Stanley's Avatar
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    Default Re: tpr drain to trap

    The 3/4" TP drain discharging thru an air gap into a waste receptor in the same room as the heater sounds and looks ok to me.


  3. #3
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    Default Re: tpr drain to trap

    Did you test it?

    mlc


  4. #4
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    Default Re: tpr drain to trap

    What about "The discharge from a relief valve shall not be trapped"?

    Looks like it directly discharges into a trap.

    I've wondered if they meant attached to an in-line trap (can't imagine that set up or the purpose it would serve) or as depicted?

    More will be revealed, I'm sure

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  5. #5
    Brandon Chew's Avatar
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    Default Re: tpr drain to trap

    Quote Originally Posted by BARRY ADAIR View Post
    What about "The discharge from a relief valve shall not be trapped"?

    Looks like it directly discharges into a trap.

    I've wondered if they meant attached to an in-line trap (can't imagine that set up or the purpose it would serve) or as depicted?

    More will be revealed, I'm sure
    The discharge from the relief valve terminates at the end of the 3/4 pipe. It discharges into an indirect waste receptor. The 3/4 pipe should not have a trap, while the indirect receptor should have one.


  6. #6
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    Default Re: tpr drain to trap

    Thanks guys. I thought it was probably okay, but wanted to make sure that the discharge into the trap is "indirect waste". Brandon and Richard confirmed my conclusions. No, I didn't test the TPR, I never do in case it gets stuck open.
    Just realized that I mixed up the order of the pipes when I described it, but I guess you all figured it out.

    Last edited by Ken Meyer; 03-21-2008 at 08:14 AM. Reason: added comment

  7. #7
    Jon Randolph's Avatar
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    Default Re: tpr drain to trap

    What it the other thing in the photo?
    What will keep that trap primed to prevent sewer gas from coming out.


  8. #8
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    Default Re: tpr drain to trap

    Yes, the trap primer will do exactly that. They are commonly used for floor drains for that purpose.


  9. #9
    Brandon Chew's Avatar
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    Default Re: tpr drain to trap

    Nothing wrong with the TPR going in there and the trap primer is probably needed.

    My questions are regarding the receptor. Does the setup in the pic meet the requirements of IRC P2706?
    • "approved type"? (how does one determine this?)
    • removable strainer?
    • installed in a ventilated space? (this one looks ok)
    • does it need a standpipe between 18 and 42 inches high?



  10. #10

    Default Re: tpr drain to trap

    this set up should work but my concern is that the ABS pipe might not tolerate the 210 degree water coming out of the TPRV if it blows off on high heat.???
    Dana

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  11. #11
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    Default Re: tpr drain to trap

    Quote Originally Posted by Dana Bostick View Post
    this set up should work but my concern is that the ABS pipe might not tolerate the 210 degree water coming out of the TPRV if it blows off on high heat.???
    Dana
    Also my concern.

    And that of the code as well. Which is why (because many times the T&P will discharge into the water heater drain pan) the water heater drain pan is only allowed to be of materials listed in Table P2904.5 Water Distribution Pipe ... and ABS is not listed in that table. ABS is only a DWV pipe.

    The discharge pipe itself is also only allowed to be of material listed in Table 2904.5 Water Distribution Pipe, and, while the trap it is draining into is not "specifically" addressed, the intent seems to be clear - if the T&P is going to discharge into it, it must be of a material listed in Table 2904.5 ... and ABS is not listed in that table.

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  12. #12
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    Default Re: tpr drain to trap

    "Which is why (because many times the T&P will discharge into the water heater drain pan..." JP

    Didn't I read somewhere you can not discharge a TPR into a drain pan?


  13. #13
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    Default Re: tpr drain to trap

    Quote Originally Posted by Dave Mortensen View Post
    Didn't I read somewhere you can not discharge a TPR into a drain pan?

    Maybe ... but it is "allowed".

    You probably read that 'it was not the smartest thing to do', but 'it is allowed'.

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  14. #14
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    Default Re: tpr drain to trap

    In this particular case, the furnace and water heater are in a closet on the inside wall of a finished basement room, on the other side of the closet wall is a bathroom. There is nowhere else for the TPR discharge to go.
    I wondered about the ABS being able to withstand the high temp as well. The waste stack that the trap is connected to is cast iron, I suppose the trap could be changed out, but I know that will never happen.


  15. #15
    Patrick Martinez's Avatar
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    Default Re: tpr drain to trap

    The WH drip pan thing is a jurisdictional thing. In Vanc. we run our pans and T&P in separate lines out of the building where practical. As to the indirect waste discharge, yes that is okay. Granted, the whole matter needs to be looked into further because of the steam that will plume out of the ind wst receptor.


  16. #16
    Stephen Houmard's Avatar
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    Default Re: tpr drain to trap

    What if the trap was in the floor. ( A floor drain ) Would that be ok? So the TPR should be 6 inches from the floor or floor drain? Can abs be in a floor drain. It would be a fine set up if we had a floor in the middle of the photo.


  17. #17
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    Default Re: tpr drain to trap

    Quote Originally Posted by Jerry Peck View Post
    Also my concern.

    And that of the code as well. Which is why (because many times the T&P will discharge into the water heater drain pan) the water heater drain pan is only allowed to be of materials listed in Table P2904.5 Water Distribution Pipe ... and ABS is not listed in that table. ABS is only a DWV pipe.

    The discharge pipe itself is also only allowed to be of material listed in Table 2904.5 Water Distribution Pipe, and, while the trap it is draining into is not "specifically" addressed, the intent seems to be clear - if the T&P is going to discharge into it, it must be of a material listed in Table 2904.5 ... and ABS is not listed in that table.
    I would not be concerned Jerry.

    The melting point of ABS material is 400 deg. F

    MSDS for ABS

    see page 1 section III


  18. #18
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    Default Re: tpr drain to trap

    Quote Originally Posted by Michael Larson View Post
    I would not be concerned Jerry.

    The melting point of ABS material is 400 deg. F
    BUT ... what is the 'softening point'?

    That 400 degrees was listed as "the processing temperature", not the "deformation temperature".

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  19. #19
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    Default Re: tpr drain to trap

    Quote Originally Posted by Jerry Peck View Post
    BUT ... what is the 'softening point'?

    That 400 degrees was listed as "the processing temperature", not the "deformation temperature".
    Fair point.

    The vicat softening point is 90 degs. C

    It would take an engineering calculation to determine if there is a real problem.

    To many variables in play.

    The water heater TPR would be open as long as the ability of the heat source to maintain a temp of 210 deg F.

    It comes down to how long is 210 deg. F water is discharged into the indirect waste receptacle and the ambient temp of the piping. While the inside of the pipe is being heated by the TPR discharge water, the outside of the pipe is being cooled by the ambient temp on the outside of the pipe.

    ABS is an approved waste pipe in many jurisdictions and as noted earlier it could just as well be below grade and suitable for a floor drain servicing the same TPR discharge.

    All this is well beyond the scope of a HI but call it out if you feel you must.
    I just don't see much hazard for this set up.


  20. #20
    Patrick Martinez's Avatar
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    Default Re: tpr drain to trap

    Hello Stephen,

    as to the floor drain, it is an approved location for a T&P, as to the piping, ABS is approved material even regarding the temperature exposure, in a second story unit, the requirement of every four feet for supports (on ABS), helps to reduce any sag though it will happen at any temp at or >120 for extended periods. The point, this being beyond the scope of the HI is probably right on...Design engineers have crafted this to work in the temps of normal exposure, the T&P lifting is not a normal condition. The WH Pan drain cannot be used an an acceptable drain for the T&P and shall be ran separately.


  21. #21
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    Default Re: tpr drain to trap

    Quote Originally Posted by Patrick Martinez View Post
    The WH Pan drain cannot be used an an acceptable drain for the T&P
    Why not?

    We just had this discussion earlier in this thread, it is allowed ... may not be the brightest thing to do, but ... it is allowed.

    Jerry Peck, Construction / Litigation Consultant
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  22. #22
    Patrick Martinez's Avatar
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    Unhappy Re: tpr drain to trap

    Hi Jerry,

    the WH Drain pan is a prohibited location for the T&P relief and shall be ran separately. 06 UPC dictates as such however, some jurisdictions may permit it, although this doesn't follow the UPC obviously. Each AHJ may have a separate auth for each situation.


  23. #23
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    Default Re: tpr drain to trap

    Quote Originally Posted by Patrick Martinez View Post
    Hi Jerry,

    the WH Drain pan is a prohibited location for the T&P relief and shall be ran separately. 06 UPC dictates as such however,

    Do you have that 2006 UPC section?

    It is not prohibited in any other code I am aware of.

    By the way, I guess the people making the Uniform Codes did not join with the other model codes into the ICC?

    Jerry Peck, Construction / Litigation Consultant
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  24. #24
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    Thumbs up Re: tpr drain to trap

    My head is spinning.
    I would recomend the home seller get rid of the H2O tank and just boil the water on the stove.
    LOL
    This is a good thread and the reason why I read this post. This keeps me thinking, looking up codes and using skills I haven't used in a while.
    Good job guys.
    Stephen Houmard


  25. #25
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    Talking Re: tpr drain to trap

    jerry,
    patrick is right, 508.5 2006 u.p.c. sorry to be the bearer of contradictory news


  26. #26
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    Default Re: tpr drain to trap

    Quote Originally Posted by brian schmitt View Post
    jerry,
    patrick is right, 508.5 2006 u.p.c. sorry to be the bearer of contradictory news
    Brian,

    I repeat my question: "Do you have that 2006 UPC section?"

    But to clarify as it was not clear ... "Do you have what that code section states?" (I.e., not just the code section number.)

    Jerry Peck, Construction / Litigation Consultant
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  27. #27
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    Default Re: tpr drain to trap

    jerry,
    section 510.8 2000 u.p.c.(new)relief valve discharge
    discharge from a relief valve into a water heater pan shall be prohibited.
    wording has not changed in the 2006 edition .


  28. #28
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    Default Re: tpr drain to trap

    Brian,

    Thank you.

    At least someone has some sense to prohibit it.

    It's not "prohibited" elsewhere, so it is done all the time, which is stupid in my opinion.

    Jerry Peck, Construction / Litigation Consultant
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  29. #29
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    Default Re: tpr drain to trap

    jerry,
    it is prohibited because of the splash effect and the subsequent damage. i am not too keen on the funnel type drains either but they can be approved. floor sinks and laundry sinks with an airgap are considered an approved location in my experience.


  30. #30
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    Default Re: tpr drain to trap

    Quote Originally Posted by brian schmitt View Post
    jerry,
    it is prohibited because of the splash effect and the subsequent damage.

    Actually, I doubt that is the reason.

    What are the listed (in that code) acceptable locations for the discharge to discharge to?

    When you list those, I will explain my first statement.

    Jerry Peck, Construction / Litigation Consultant
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  31. #31
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    Talking Re: tpr drain to trap

    jerry,
    608.5 says ..."and shall extend to the outside of the building...such drains may terminate at other approved locations" i just gave you what i as an ahj consider other approved locations. it is just my opinion which as we know are like a$$hole$,everyone has one. feel free to express one!


  32. #32
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    Default Re: tpr drain to trap

    Quote Originally Posted by brian schmitt View Post
    608.5 says ..."and shall extend to the outside of the building...such drains may terminate at other approved locations"
    Quote Originally Posted by brian schmitt View Post
    it is prohibited because of the splash effect and the subsequent damage.
    The reason I doubt that is the reason is that in all other (correct that, most all other) AHJ *want* the discharge to be readily visible by the occupants (as says the code) and that they would prefer to have it discharge in the center of the living room if they could get away with it (not my words, theirs, I've been told that by many AHJs).

    Jerry Peck, Construction / Litigation Consultant
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  33. #33
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    Default Re: tpr drain to trap

    jerry,
    i could terminate the drain behind my house where no one would ever see it because it is not too accessible and still meet code. ya think maybe another reason for outside termination besides seeing it would be safety? having hot water splash on the skin could burn! hmmmn! maybe that's why it has to terminate 6" to 24" above grade pointing down. i see safety as the main consideration,not visibility. just an opinion!


  34. #34
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    Default Re: tpr drain to trap

    Brian,

    In the IRC and other codes, the T&P discharge line *is required* to discharge *in the same space as* the water heater, no allowed to discharge to the outdoors.

    Years ago, discharging to the outdoors was the preferred method, however, with more water heater still exploding, most plumbing officials/inspectors think blowing it off inside where it can be seen (hence 'in the living room') is preferred.

    My position is that, once it blows off, the danger is gone (it is only dangerous if it does not blow off - so blowing it off in the living room only tells the occupants 'oh, hey, you were almost killed, but it's okay now').

    With the T&P blowing off to the outdoors (my preference), the incoming cold water replaces the outgoing hot water, dropping the temperature to within safe limits, and, when they go to use hot water and there is none, that is when they will call the plumber.

    No need to flood the garage/interior just to get them to call the plumber.

    The plumbing inspectors think that the water will make the occupants turn the power / gas off to the water heater, no, leaking water will only make them turn the water off, closing the system down even further, making it more explosive.

    Jerry Peck, Construction / Litigation Consultant
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  35. #35
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    Default Re: tpr drain to trap

    You make some good points Jerry.

    A better solution to the problem would be a Watts 210 that shuts down the gas supply when the temperature is exceeded.
    Of course this is for gas fired units but I can't imagine a similar units couldn't be developed for electric water heaters.


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