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Thread: Trap primer questions

  1. #1

    Default Trap primer questions

    I did 1/2 of my apprenticeship way back in the early 80's. (I should have finished, then I would probably be off today and not in work preparing for a trial....) I cant remember the requirements for trap primers.


    First I have two "showers" back to back to each other. One is actually going to be a laundry room for stack w/d. My question is, do I need to prime the floor drain if its trapped. I will be using a seperate stack for vent and wastewater discharge. Or can I trap the run for both the disharge and floor drain? See attached picture.
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  2. #2
    Moderator & Master Plumber hj's Avatar
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    Default primer

    You have to have a trap primer because it is trapped and if there is no reliable source of water flow into the trap to keep it from drying out. As shown, neither drawing is acceptable. The upper one does not have a vent for the right hand trap, and the bottom one uses a running trap which is not acceptable.

  3. #3
    Forum Admin, Expert Plumber Terry's Avatar
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    Each "fixture" will have it's own p-trap, and each p-trap will be vented.

    Those vents can be tied together at 6" above the highest fixtures "flood level". Flood level is that point at which the water flows over the edge. For a toilet, that would be the bowl, for a kitchen sink, it would the the edge of the sink and over the counter. You know that the water won't get higher than that. At least not 6" higher.

    Fixtures that don't get regular water, like the one under a washer, or a floor drain, require that the traps get "primed".

    They make several types of devices for that purpose.

    If traps are not vented properly, they will siphon dry.
    When they siphon out, your next post will be

    "I have a bad smell coming from the ( bathroom / washer room / mud room ) "

    Something like that.
    The reason we plumb the way we do is for two reasons,

    1) maintaining pure and safe drinking water.
    2) having a system that drains well and can be maintained to drain well.
    3 elimation of bad odors.
    4) sanitary prevention from the spread of germs.

    I don't know why homeowners would want to shortcut these safety factors in their own homes?
    If you want to know what it would be like without licensed plumbers, go to one of the third world countries where everyone has to buy drinking water from bottles, the smell of stinking waste fills your nostrils as you look out over what should be a beautiful scene.
    Children that don't live to be adults.
    I was horrifed by the plumbing I saw.
    I would hate to see our country go that route.
    Last edited by Terry; 03-26-2005 at 12:26 PM.

  4. #4

    Default you guys are hard on me

    Terry,

    I remember that class from apprentice school, they tied legionaire's disease in with it, if I'm not mistaken. It was right after teh class with the exploding water heater...( i bet they still use the same film.)


    I do not beleive I expressed myself correctly. I'll do a better drawing.

  5. #5
    Forum Admin, Expert Plumber Terry's Avatar
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    There was a water heater in Washington that landed a block away.

    It went through the roof and still went that far.

  6. #6

    Default New picture

    Terry:

    My apprenticeship was exclusively done on the industrial side of the trade. Mostly mechanical joint/weld/vic/melt stuff. I never got the opportunity to do residential work.

    I understand I now I can't use a running trap. I wanted to do that to eliminate the need to use primer.
    I think I have a solution for that though.


    My question is do I need to take off the vent downstream of the trap?

    Or can I use the layout as in the revised drawing?
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  7. #7
    Forum Admin, Expert Plumber Terry's Avatar
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    You can't wet vent the washer over the floor drain, and you can't wet vent the washer and floor drain over the toilet.

    Is this being inspected? I hope so.

    The washer and floor drain should tie in below the toilet.

    The washer, the way you have it would most likely siphon out the floor drain unless you are considering running 3" pipe between the washer and the main stack.
    UPC code does not allow for a washer to be wet vented though.
    They only allow either "(1) or (2) fixture unit" fixtures to be wet vented.
    A washer is considered be (3) fixture units.

    I would put another wye in there and seperate the floor drain and the washer.

    If you decide not to wet vent, then you could use 2" pipe, and tie the vents together up higher.
    http://www.iapmo.org/common/ROP2004...reprint/ch9.pdf

    the the floor drain and the p-trap of the floor drain with an inlet for the primer.

    This picture below uses wye fittings for the floor drain and for it's venting.
    The vents tie together higher.
    Attached Images Attached Images  
    Last edited by Terry; 03-26-2005 at 02:53 PM.

  8. #8

    Default I think I have it.

    I have half a mind to run the pipe from my floor drain directly above the basement drain. Its only for the emergency situation where the washing hose breaks.


    How about this revised drawing. I was using 3 inch btw.
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  9. #9
    Forum Admin, Expert Plumber Terry's Avatar
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    Default


    Check this drawing.

  10. #10

    Default thanks

    I think we drew the same thing from diff perspectives.

    Sorry for the initial cerebral flatulence. I appreciate your input and advice.

    I see you are from out west. Nice part of the country. If your ever in Phila give me a yell.

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