under joist plumbing

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by segal46, May 6, 2014.

  1. segal46

    segal46 a/v technician

    Messages:
    27
    Location:
    montreal , QC
    Hi all,
    just need some clarification, I will be moving my kitchen sink to another wall, owner of an older duplex, i dont see myself drill holes in the floor joist beneath(2x8), i will only drill 2 holes for the 1/2 inch water supply, but the drain which is 2 inches I want to put it beneath the joists, to my questions, 1st what distance will i need, seeing it is a 2 inch drain with a slope of 1/4 per foot at 3 feet distance is 3/4 inches. i figure a 4 inch beneath the joist is enough, i am adding 2 photos,does my workaround make sense or should I not touch it with a 10 foot pole.

    1st picture is existing plumbing, below it is what I want to work on, any suggetons will be aprecciated.

    thanks in advance

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    Last edited: May 6, 2014
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,488
    Location:
    Cave Creek, Arizona
    If I am looking at both photos correrctly, neither one is correct. The upper one has the connection to a the second floors drain without an intermediate vent and the second one has the vent connecting to that drain. Neither is permitted. The line under the joists can be run any way you want to as long as it slopes properly.
  3. segal46

    segal46 a/v technician

    Messages:
    27
    Location:
    montreal , QC
    Thx for the response,
    hmm.. my house was built this way (1965). Been here for 15 years havent had a problem..this may be an amaturish question, but can it be vented through another pipe or directly to roof? If so would this make it feasible? Will try and follow it to the upstairs apartement to see where it leads.

    again thx for the response
  4. Terry

    Terry Administrator Staff Member

    Messages:
    14,891
    Location:
    Bothell, Washington
    In Canada, you may have a trap below the sink cabinet that is vented.
    You can't dump the upper floor into the trap. You will need to open the wall below and connect below the trap that is under the sink.

    The first drawing is kind of marked up, so it may be hiding what is really happening.
  5. asktom

    asktom Member

    Messages:
    529
    Location:
    Victor, MT
    Is it possible the line going up is the vent and not the drain from above?
  6. segal46

    segal46 a/v technician

    Messages:
    27
    Location:
    montreal , QC
    will look into this tonite..thx for all the responses
  7. Terry

    Terry Administrator Staff Member

    Messages:
    14,891
    Location:
    Bothell, Washington
    At any rate, I would not put a 2" waste line through a 2x8 floor joist. Under the joist would be the right location, and 4" of space should work. Now you just have to make sure about venting.
  8. segal46

    segal46 a/v technician

    Messages:
    27
    Location:
    montreal , QC
    yes, thx..i will go the route of under joist..as for the drain part of this post, I followed it under and nothing but striaght pipe to ground and for the same drain that comes from appartement above, it serves as a drain not only for my sink but the upstairs sink and washer, though it seems the same piping goes up and out to the roof, can this serve a double purpose of vent and drain?? maybe it is split somewhere above or behind the wall..I figure its worked for 50 years, something has to be right....or am i wrong..lol
  9. Terry

    Terry Administrator Staff Member

    Messages:
    14,891
    Location:
    Bothell, Washington


    Yeah, pretty funny. When the washer pumps out downstairs and siphons your kitchen trap, and you wind up with smelly sewer gas in your kitchen, it's all good. Most people just assume that that's how a kitchen sink smells. Bad :(
    Maybe you can live with that, but that doesn't make it right. When I used to visit the family property in Canada, we used an outhouse and carried water from the lake in pails. But like you, we did it for years, so it must of been right.

    I have also seen deep sinks in the new remodeled kitchens where the installers just leave off the p-trap because the drains are too high. They smell horrible too. Though the homeowners don't seem to care. They just assume that kitchen sinks smell when you get near them.

    The upstairs washer and sink does not work as a vent for the downstairs sink. Not in any code.
  10. segal46

    segal46 a/v technician

    Messages:
    27
    Location:
    montreal , QC
    baffled...though I believe you are right...never had any odour in last 15 years,nothing...so i will open a wall in the appartement upstairs hoping to find an adjoining vent that goes to the roof, because i am sure there is one going up there....just nothing downstairs...any suggestions?
  11. Terry

    Terry Administrator Staff Member

    Messages:
    14,891
    Location:
    Bothell, Washington
    People without p-traps don't seem to notice odors either. I notice, because I'm used to plumbing that works. My nose isn't that bad yet.

    You could run a load of wash upstairs, and then pull the p-trap below and see if it's holding water though. That would be a good test.
    Last edited: May 7, 2014
  12. Reach4

    Reach4 Active Member

    Messages:
    2,076
    Location:
    IL
    I would try looking down from the roof to see where vents go rather than opening walls to find a vent. I wonder if you could lower a noise maker on a cord to help locate where a vent is with respect to the inside walls.

    If the vent pipes are not seen to go vertical very far, perhaps a trip to the attic will give some useful info.

    Just an idea.
  13. Terry

    Terry Administrator Staff Member

    Messages:
    14,891
    Location:
    Bothell, Washington
    I'm 62 years old, and have never gone up on a roof to look down a vent to figure out how a home is plumbed. How does that work? Looking down a pipe on the top of a roof.

    What I did do today, is install a Kohler cast iron shower pan weighing hundreds of pounds. I set the P-Trap in place, laid out two 2x4's, droped the pan down, pulled out the 2x4's and spun the compression ring on the Oatey shower drain down on the rubber collar. Pretty smooth.
    Then I played a double header softball game with my son Jamie. The first game we won 38-6 in four innings. The second game was close, but also a win.
    I had five hits in four innnings in the first game.
    Last edited: May 7, 2014
  14. segal46

    segal46 a/v technician

    Messages:
    27
    Location:
    montreal , QC
    yes the p trap is holding water downstairs, while a load was done in upstairs appartment, so no siphoning going on...all copper 2 inch tubing..when copper was still affordable. So if it is holding the water as you suggested, now what....I have respect for the trade and want to do it right the first time...I have no time for any sports until my wife stops badgering me to "get it done"..lol
    So thanks for taking the time to make this a little simpler...

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  15. Reach4

    Reach4 Active Member

    Messages:
    2,076
    Location:
    IL
    If the roof was readily accessible, it was not too pitched, and there is no attic, I would try using a bright flashlight to see what I could see. Of course it would help if the vent was 4 inches, and went straight down for a good while. It seems preferable to starting with opening a wall in the apartment upstairs hoping to find an adjoining vent that goes to the roof.

    I'll bet you have run snakes from the roof.
  16. Terry

    Terry Administrator Staff Member

    Messages:
    14,891
    Location:
    Bothell, Washington
    I don't. I don't do drain cleaning.
  17. segal46

    segal46 a/v technician

    Messages:
    27
    Location:
    montreal , QC
    nor do I but can my thread be answered.....
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