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Thread: Drain location for kitchen sink rough-in

  1. #1
    DIY Member JMingrone's Avatar
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    Default Drain location for kitchen sink rough-in

    Hi all,

    I'm roughing in for a new kitchen sink/base cabinet and was wondering what the experts recommend for where the drain should be brought up. The kitchen is gutted, so I have a lot freedom on where to put it, except it's a easier from down below in the basement to put it no closer than 16" off the wall. This would put it more towards the front of the base cabinet Is this ok?

    As far as left-right position goes, i saw this picture on the site which shows the drain coming up on the side, rather than the center:

    Name:  sink.jpg
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    This is pretty much what I will have except my dishwasher will be on the right. This looks pretty good, so what i'm thinking is bringing the drain up all the way to one side and forward of the sink center. Anyone see any flaws with this design?

    Thanks

  2. #2
    DIY Member JMingrone's Avatar
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    Sorry, dishwasher is to the LEFT of the sink...

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    Moderator & Master Plumber hj's Avatar
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    YOU want the drain on the side that is farthest from the disposer. If you are bringing the drain up through the floor, how will you avoid having a ""S" trap? The dishwasher location is irrelevent.
    Licensed residential and commercial plumber

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    Forum Admin, Expert Plumber Terry's Avatar
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    We put the drain in the back wall.
    The drawing above is just meant to show how things drain. Which is hard to do with a front on picture.

    for a deep sink, we stub out the sink trap arm at 16" above the floor.
    You you have a single bowl and disposer, then offsetting either way 8" works.
    If you have a double bowl, then aiming for the bowl drain opposite of the disposer works fine. You can miss by a few inches and the swivel of the trap will still pick it up.

  5. #5
    Test, Don't Guess! cacher_chick's Avatar
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    The drain is in the wall because that is the only logical place to continue the vertical section of vent. The vent must run vertically upward at least 6" higher than the rim of the sink. From that point it can continue to run vertical or horizontal if need be to get up through the roof.

  6. #6
    DIY Member JMingrone's Avatar
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    Thanks to all who replied.

    RE the drain in the wall: Actually, that's where it originally was. When I demoed the wall I discovered the old wall drain (1-1/2" galvanized pipe) which someone capped off with a dish rag (no kidding). Unfortunately, the threads were rusted out, so I sawz-all'd the stub off flush with the wall, and moved to plan B which was to drop the drain thru the floor like the previous renovator did, 5 ft to the right (I'm moving the sink back to its original location).

    So looks like I have at least 3 options:

    1) Figure a way to adapt some kind of fitting to the sawed-off stub and put the drain in the wall (it's 13" off the subfloor). Is there an acceptable way to do this?

    2) Cut out the old 1-1/2" T and put something else in its place to drain thru the wall. What would go there?

    3) Cap off the wall drain and go back to the original plan of dropping the drain thru the floor. The previous setup had an "S" trap as hj noted, and I suppose i'd need to do the same. Are "S" setups "ok" or to be avoided?


    Interested in suggestions.

    Thanks,

    Jay

  7. #7
    Test, Don't Guess! cacher_chick's Avatar
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    S-Traps are not permitted and will fail any plumbing inspection. There is no approved way to install a drain going down without a vent going up.

    A plumber would install PVC pipe in the wall, with a sanitary tee around 15" off the floor. The sanitary tee would have a trap adapter installed which would connect to the sink's trap arm. The vent would run upward from the top of the sanitary tee. It can tie into another vent which goes through the roof, or can be run through the roof on it's own. The drain would run down from the bottom of the sanitary tee, and into the basement or crawlspace to tie into the existing drainage system.

    This is how plumbing is done. Every P-trap must be vented to prevent siphoning.
    When a trap siphons, sewer gas, drain flies, and other things you do not want will come back into your house.


    Here is a nice link to Bert Polk's plumbing tips
    Last edited by cacher_chick; 11-20-2012 at 07:14 PM.

  8. #8
    IBEW Electrician big2bird's Avatar
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    Quote Originally Posted by Terry View Post
    We put the drain in the back wall.
    The drawing above is just meant to show how things drain. Which is hard to do with a front on picture.

    for a deep sink, we stub out the sink trap arm at 16" above the floor.
    You you have a single bowl and disposer, then offsetting either way 8" works.
    If you have a double bowl, then aiming for the bowl drain opposite of the disposer works fine. You can miss by a few inches and the swivel of the trap will still pick it up.
    I need to ask here. I offset my in wall work 10" to the left for the dual bowl kitchen sink, but alas the disposal side of the sink is on the left as well. Am I screwed?

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    DIY Senior Member kreemoweet's Avatar
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    JMingrone, you say you have a sawzall, so put it to good use like so: cut out ALL of that old, tired, clogged-up, undersized
    1 1/2 galvanized drain line to where it connects with a big house drain. Replace with 2 in plastic drain with sanTee/trap adapter
    for the sink to connect to. Probably there's an 1 1/2 galvanized vent line above that in decent condition, which you can connect
    to with a rubber coupling. Then you'll have a normal drain setup which won't require cabinet surgery.

  10. #10
    DIY Member JMingrone's Avatar
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    kreemoweet: That's the ticket. Was trying to avoid un-sheetrocking the wall, but that's the right way to do this thing. Yes there's a 1-1/2" galvanized vent line in good condition above the buggered up T. So I'll saw off just above it, put plastic below and join them with a rubber coupling. Probably move it up to 16" off the floor as Terry suggested.

    Funny thing is, yesterday, I found the same setup in an adjacent half-bath, so now I have 2 to do!

    Thanks,

    Jay

  11. #11
    Moderator & Master Plumber hj's Avatar
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    We would do better with a picture, but I assume there is a tee in the wall and you cut off the "arm" coming out to the sink, (except maybe because of a "don't stand there, do something" mentality). I do not know why you would have cut if flush with the wall, when the proper thing would have been to unscrew it from the tee and install a new pipe, assuming it is low enough to connect to the sink. The best option based on what you have written, which might not be exactly what you have, would be #2. Remove the tee and install a NEW tee in its place.
    Licensed residential and commercial plumber

  12. #12
    DIY Member JMingrone's Avatar
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    Hj, all that was left in the wall was the unused T with bad threads ( stuffed with a rag). Only reason i sawed it off was so it wouldn't protrude into the new sink base. I intended to just plug it with something better than rag when I figured out how to do it.

    My plan now is to open the wall again, saw it out, put in a new plastic santee and run 2" plastic down to the drain line in the basement as kremo suggested. Got the parts at Home Depot this afternoon, so looks like it will all work and makes more sense than going thru the floor with a "S" trap.

    Jay

  13. #13
    DIY Member JMingrone's Avatar
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    OK, so a few final questions:

    1) In the kitchen, the vertical drain/vent pipe is 2". Two legs of the santee are 2" to adapt to the existing pipe, but does the third leg get fitted with a 1-1/2" P-trap adaptor?

    2) Same question for the lav: The vertical pipe is 1-1/2" so, put a 1-1/4" adaptor?

    3) For the kitchen, since I'm cutting out the old wall T, I can change its height, so ideally, how far below the bottom of the sink should the stub be coming out the wall?

    Thanks,

    Jay

  14. #14
    Test, Don't Guess! cacher_chick's Avatar
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    Kitchen sink uses a 1-1/2" trap, and a bathroom lavatory uses a 1-1/4" trap, so yes, the trap adapter should be sized accordingly. The lav can be plumbed with 1-1/2, but the tailpiece is normally the 1-1/4, so would require a reducer when the connection is made to the tailpiece.

    A lot of houses are going to deeper sinks and then a disposal, making the need for a relatively low trap arm. 15" off the floor is becoming pretty common.

    Most old sinks using galvanized pipe were all done in 1-1/2". Do remember that the measurement is the inside diameter of the pipe, not the outside.

    Happy Thanksgiving.

  15. #15
    DIY Senior Member kreemoweet's Avatar
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    I would suggest stubbing out with 1 1/2 pipe from the santee and leave the fitting of the trap adapter until after the
    sink and other appliances are installed, and the tubular drain stuff is going in. Sometimes the standard-length tubular trap
    arms come up short, and longer ones are hard to find. This also leaves you the option for putting a bend in the trap
    arm, which is sometimes necessary. Ditto for the lav drain.

    There is no drain height which works universally well with all combinations of sinks, drain outlets, disposals, etc. If you know
    what's going in there beforehand, you can usually work out a good height for that combo. Otherwise, as Terry has mentioned,
    16 in. above finish floor is a good guess.

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