Kitchen sink, p-trap and long horizontal drain

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Trymor, Sep 29, 2021.

  1. Trymor

    Trymor New Member

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    Sep 29, 2021
    Location:
    Toronto, ON Canada
    Hi! First time posting… please be kind. I’ve just finished building my own kitchen, which was plumbed too early in the process and in order to get my cabinetry on I had to rip out what the plumber did without the option of getting him back in here. Additionally he didn’t put the dishwasher wye on the best side and he put it on past where the ptrap would be, which I think is a no-no? It’s not a straightforward drainage set up as far as I can tell so please bear with me.

    The sink drain is currently a stub in the bottom of the back of the cabinet, and it bends 90° under the cabinet, slopes down to the right about 30” and connects to the vent and drain in the wall below or at floor level (see drawing).

    28178933-61A9-4E8E-B2C0-063DA5E33F48.jpeg

    My plan is to connect the continuous waste for the double sink with the dishwasher wye on the vertical where the two drains meet, then the p-trap with clean out connecting to… ??? an arm going into a 90° elbow leading down into the stub in the cabinet floor? Is that right? How high should the vertical out of the floor and the trap be? (See drawing for clarification).

    Note that I have experience with very basic sink plumbing but I’m not too familiar with all the ins and outs of venting etc. This setup feels very weird to me, but I hope it’s not problematic. Please help!

    image.jpg
     
  2. Jeff H Young

    Jeff H Young In the Trades

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    you've got a s trap not allowed the trap needs to connect to a horizontal trap arm which cannont be turned vertical
     
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  4. Trymor

    Trymor New Member

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    Thanks, is there a way to correct this issue given that this is an older home and I can’t modify the DWV that’s already installed?
     
  5. Terry

    Terry Administrator Staff Member

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    You really should add an AAV there for venting. Off of the trap, it would go to a santee, with an AAV 4" higher than the trap arm.

    [​IMG]
     
  6. Trymor

    Trymor New Member

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    omg Terry Love himself… thank you so much, your pic makes it very clear.

    can you just help me understand why an AAV is necessary? (Ie. why isn’t the fact that the drain is connected to the roof vent nearby sufficient air intake?)
     
  7. Terry

    Terry Administrator Staff Member

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    Plumber
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    [​IMG]

    [​IMG]

    [​IMG]
     
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  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    When the drain is configured properly, the vent will break the siphoning effect and allow the p-trap to retain the water, and provide it's function of blocking sewer gasses from escaping, as the trap won't be siphoned. An AAV, although not the preferred method, can perform that task. One reason why it's not the preferred method is that they do eventually wear out and need to be replaced, whereas an atmospheric vent won't.

    An S-trap can actually drain too well, and with nothing to break the siphon, can end up dry under some conditions, making the trap somewhat useless.
     
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  9. Trymor

    Trymor New Member

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    Thank you all so much! This community is amazing.
     
  10. Trymor

    Trymor New Member

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    Sep 29, 2021
    Location:
    Toronto, ON Canada
    Hi all, thanks again for your help. I’ve done some dry fitting and was hoping you all could let me know if this assembly is legit before I start cutting the pipe lengths… I’ve used a few extra fittings to move the continuous waste further back into the cabinet… I got an AAV to add on top of the vertical part of the drain after the trap.

    Key questions:
    - are the horizontal 90° bends ok?
    - is it ok to mix PVC pipe with ABS? (I had tubular PVC left over from my IKEA vanity)

    thanks in advance!

    5A8682C1-1D0A-48EF-BD08-6E72CC3597ED.jpeg
     
  11. John Gayewski

    John Gayewski In the Trades

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    Iowa
    Not real legit. You have a tee in the wrong orientation.
     
  12. Trymor

    Trymor New Member

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    Toronto, ON Canada
    Thanks for responding. Are you referring to the tee in the centre connecting the two white PVC tubes? This is part of the centre outlet continuous waste assembly I purchased and it’s in its original orientation (see image attached). What’s not right about it? E1709B8B-FD60-4F5C-BD62-57E3A51E15AF.png
     
  13. Reach4

    Reach4 Well-Known Member

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    Location:
    IL
    1. I would put a trap adapter at the sanitary tee. I would use all slip and no glue between that and the sinks.
    2. The AAV should be at least 4 inches above the santee input.
    3. To make room for the AAV, I would not route the drainage so close to the wall.
    4. I think your baffle tee is OK if you use that configuration. You will see a baffle that inhibits water shooting across horizontally.
    5. Check out the picture in post #4. Many prefer that to the horizontal baffle tee configuration. It uses a baffle tee with different baffling..
     
  14. Trymor

    Trymor New Member

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    Thanks!

    1) in my configuration the trap adapter is under the centre outlet, transitioning from the tubular pipe to the standard 1 1/2” abs. so that I could add the dishwasher wye which I could only source in the 1 1/2” ID. What would the purpose of a trap adapter at the sanitary tee be?

    2) it will be :)

    3) The pic you posted is the same one Terry posted earlier that set me on the right path… unfortunately I couldn’t easily source some parts, so configured it as I did: I have the two horizontal pipes from the sink strainers connecting into the centre outlet, which goes into the trap adapter, into the dishwasher wye and into the trap. All threaded connections up to the trap adapter and cemented from that point forward. I have yet to cut down the arms coming out of the sink strainers by an inch or so, which will bring the assembly a couple inches in front of the drain which is at the very back of the cabinet with enough room for the AAV.

    I *think* that addresses everything you mentioned; my husband is concerned the dishwasher will be draining too far down the line (ie. not high enough above the p-trap) but I don’t have enough height under the deep sinks and strainers unless I can find a dishwasher wye that will connect to the tubular pipe (which I can’t) and put it on the horizontal.
     
  15. Trymor

    Trymor New Member

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    I didn’t see these points when I replied:
    are you saying the baffle tee the way I have it (with the 90° elbows) won’t work well? Or are you saying you’re not sure if the tee I have there is a baffle? (It is - I think … it has kind of walls inside where the two inlets join)
     
  16. Reach4

    Reach4 Well-Known Member

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    Location:
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    a. To allow easy adjustment during installation or repairs.
    b. To allow easy cleaning if needed by disassembly.
    c. To allow a spot to rod if you don't have a cleanout.

    I am not sure if this works or not. Is it tailpiece only or can it be used as an extension? https://www.lowes.ca/product/under-...-joint-branch-tailpiece-58-in-od-outlet-42035
    https://www.amazon.ca/Keeney-35-8WK-Tailpiece-Connect-Dishwasher/dp/B000DZBLXC
     
  17. Jeff H Young

    Jeff H Young In the Trades

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    looks like those wye branches can be used either way as an extension type or directly on a basket strainer .
    We usually buy either "nut up" or "nut down" and supply house guy knows exactly what we mean. 2 different configurations rather than these universal ones that reach4 shows
     
  18. Trymor

    Trymor New Member

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    Sep 29, 2021
    Location:
    Toronto, ON Canada
    That’s what I figured after I gave your comments some thought… glad to know my intuition is starting to work :)

    I purchased one of these yesterday thinking I could use it on the horizontal but I wasn’t confident… it has a flange, could I cut it off to use in the slip connection to the elbow? Is the baffle ok to use horizontally?
    8B1DE0B3-F2FE-4E9A-BC3E-491A42A66F5D.jpeg 0CF591AF-1B59-42F4-B619-64433F908DC1.jpeg
     
  19. Trymor

    Trymor New Member

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    hi Jeff, could you rephrase this in lay terms for the noob?
     
  20. John Gayewski

    John Gayewski In the Trades

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    Yeah don't use that.
     
  21. Reach4

    Reach4 Well-Known Member

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    Sep 25, 2013
    Location:
    IL
    Not sure.
    I think so. I was a bit surprised to see the baffle. Some don't have baffles, and some do. The chrome-plated brass ones normally do not, and they can be mixed. Mixing may be aesthetically displeasing.
     
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