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rough drain plumbing for kitchen sink

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  • rough drain plumbing for kitchen sink

    I'm getting my kitchen replaced really soon and I've already torn out the original builder cabinets. While they're out, I'm taking the opportunity to improve things. The old drain pipe ran about 4' horizontally through the cabinets from the sink to the corner of the kitchen, represented by the red line on the picture. This of course meant occupying space in those cabinets and putting holes in the cabinet sides and bottom for installation, which the original installers did in the most expedient way possible (possibly with a claw hammer).

    I'd really like to not have those pipes running through my new cabinets if possible, but I don't know if there was a good reason that the original plumber went horizontally through 3 cabinets instead of going down to the basement. The joist bays are all open in the basement, and ideally, I'd rather have the drain and vent pipes running under the floor, represented by the blue lines in the picture. So straight down from the trap, through the floor to a 90 degree elbow and across to the original pipe, keeping the original vent configuration in the corner. Is there any reason not to do that?

    Kitchen.jpg
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  • #2

    Re: rough drain plumbing for kitchen sink

    Re: rough drain plumbing for kitchen sink

    If I remember correctly, the plumbing code states the distance from the bottom of the sink to the trap cannot exceed 36 inches, which is why the rough-in is done above the floor instead of below the joists.

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    • #3

      Re: rough drain plumbing for kitchen sink

      Re: rough drain plumbing for kitchen sink

      The trap on the old installation was right below the sink in the cabinet and then went horizontally about 3' after the trap before getting to the vertical in the corner where the vent is. What I was thinking of doing was still having the trap above the floor in the cabinet but then instead of running horizontally as in the red dotted line, running straight down through the floor after the trap and then horizontally under the floor to that same corner and using that same vent. Obviously if that's likely to cause problems (or break the code), I'll just live with the pipes running through the cabinets as they were, but I'm hoping to put a lazy Suzan in that corner and the pipe sticking up through it wouldn't be much help.

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      • #4

        Re: rough drain plumbing for kitchen sink

        Re: rough drain plumbing for kitchen sink

        ive seen both scenerios many times

        I believe that the "blue" option does not meet the plumbing code, but I have replaced many kitchens using the existing "blue" system with no problems

        another option is to move the "red" system into the wall cavities, bringing it out under the sink and using a regular p trap
        my shop is a beaver lodge
        steve, sarnia, ont




        1940's Craftmaster Lathe

        https://www.facebook.com/artistryinwoodca/

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        • #5

          Re: rough drain plumbing for kitchen sink

          Re: rough drain plumbing for kitchen sink

          Originally posted by Derek S View Post
          I'd rather have the drain and vent pipes running under the floor, represented by the blue lines in the picture. So straight down from the trap, through the floor to a 90 degree elbow and across to the original pipe, keeping the original vent
          I would run down thru the floor like your blue lines. Put a p-trap under the sink, place a cleanout between the trap and the floor, use 2 - 45 degree elbows instead of a 90 (easier to get a snake thru 2- 45's to clear a blockage).
          ...Terry

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          • #6

            Re: rough drain plumbing for kitchen sink

            Re: rough drain plumbing for kitchen sink

            Your pic seems to show the vent line stubbed at the right, which normally should be directly behined the sink in the wall. I think Noel is closer in that the vent line has to be up higher but also the trap has to be closer. It appears the orig bldr misplaced the drain in rough framing and made up for it by going to the right.

            A visit to the bldg dept. front counter to informally discuss might be advisable.
            Start slow; wind down gracefuilly

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            • #7

              Re: rough drain plumbing for kitchen sink

              Re: rough drain plumbing for kitchen sink

              The vent line dives into the wall with a pair of opposing 45 degree elbows at the top of what you can see in the picture, proceeds straight up, then through a bulkhead over the original cabinets to the centre of the kitchen, then up into the joists and across the house 20 feet to the far end of the joist bay and up to connect (presumably) with the upstairs bathroom drain vent. They couldn't go into the wall behind the sink because there is a window there, and I suspect that going all the way to the corner put them closer to that bulkhead so they didn't have to go horizontally through the outside wall, which is only 2x4 studs.

              There are some pretty questionable things about the plumbing in my house and the more I've seen about what these guys did, the more I wonder how it could have passed an inspection. The cold water supply to the kitchen sink used to have about 7 90 degree elbows on it running in all directions - it looked like somebody was teaching somebody else how to solder pipe and they decided to use the guy's creation. I wish I'd snapped a picture. The kitchen sink also had the hot and cold water supplies reversed, and so does my ensuite's shower. Given all the strange and shall we say ... counterintuitive ... things that I've found about what they did, I've come to doubt practically everything they did with the plumbing, hence this thread. I can't easily distinguish between the things they did to comply with code vs. the random but harmless vs. totally wrong things.

              I really wish there was a book like "Electrical Code Simplified" for plumbing and building codes but alas... I looked and haven't had any luck finding one. Recommendations there are definitely welcome because I'd really love to get better informed on those things.

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              • #8

                Re: rough drain plumbing for kitchen sink

                Re: rough drain plumbing for kitchen sink

                First, just to clarify if I may,

                They couldn't go into the wall behind the sink because there is a window there
                a window above the kitchen sink (not shown) is pretty much the norm and the vent pipe simply goes around the window and continues upward, using of course a slight slope on the horizontals to flow air.

                As to books, Depot has a couple has a couple that might be helpful, and while they would quiote thge code, they would be in general compliance with their advice, and in some case make reference to national codes. Also other book stores and Bldg centers.

                This of course after your further decription, further justify an informational discussion at your local building dept.
                Start slow; wind down gracefuilly

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                • #9

                  Re: rough drain plumbing for kitchen sink

                  Re: rough drain plumbing for kitchen sink

                  If you go down through the floor make sure your P trap under the sink is really a P trap with venting and not an S (illegal) trap.

                  billh

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                  • #10

                    Re: rough drain plumbing for kitchen sink

                    Re: rough drain plumbing for kitchen sink

                    You'll have to cut open the wall where the vent goes up cut it off in the wall then with a coupler drop it straight down & tie it back together with the drain under the floor joist. This will avoide the use of a cheater vent & keep everything above board.

                    Billr

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                    • #11

                      Re: rough drain plumbing for kitchen sink

                      Re: rough drain plumbing for kitchen sink

                      Well I definitely appreciate everybody's thoughts on this. I went and talked with the cabinet installers and they suggested that since the cabinets I'm getting have short legs and about 4 1/2" underneath, the simplest thing to do is to just bring the horizontal portion down to just above floor level with a bit of a downward slope so it can run under the cabinets behind the legs and put an elbow to bring it up to the trap. Bill R. and billh mentioned a couple of particularly useful search words that lead to some diagrams that clarified a few points for me, so thanks for that.

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                      • #12

                        Re: rough drain plumbing for kitchen sink

                        Re: rough drain plumbing for kitchen sink

                        Creative HomeOwner Books do a pretty good plumbing or elec Book the plumbing book ISBN is 1580110851 , I may have got it at HDepot or Rona or possibly Amazon.

                        M.

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                        • #13

                          Re: rough drain plumbing for kitchen sink

                          Re: rough drain plumbing for kitchen sink

                          Can't you use the newer code qualified vent header gizmo that terminates under the sink but above the trap. I had my plumber install one for a client last week. Can't remember what it's called.
                          "Do it Right!"

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                          • #14

                            Re: rough drain plumbing for kitchen sink

                            Re: rough drain plumbing for kitchen sink

                            Typically called a cheater vent but also called a Air admittance valve. Allowed in a kitchen island under section 2.5.9.2 but an inspector might take issue in the above case (just because of the proximity to a proper vent). That being said, it would work fine.
                            ---
                            Randy

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