Wall drain location too high

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Mike__B

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Hello all, I've seen some suggestions here and on other sites about this issue. We have new cabinets, countertop, and deeper sink. The wall drain was installed about 20" above the finished floor, and now the trap weir would be 2" above the disposal outlet.

My wall drain for the kitchen is under a window, it runs horizontal about 3 feet to a sanitary tee, drain and vent from there. this is best guess from what I can see, I'm about 99.923% sure.

Here is a diagram of what exists today:
CurrentKitchenDrain.jpg

Solutions I've seen discussed include:
  • Install a new, lower horizontal drain
    • I would need to at a minimum...
    • remove drywall behind dishwasher (to the right of sink), install new tee
    • drill through a king, jack, and cripple stud
  • Get a more shallow sink
    • This is financially not feasible with the countertop and undermount
  • Get rid of the disposal
    • My wife would never let this go
The idea I have is to put a new vertical drain pipe into the basement (at "B"), and catch the existing drain line there (at "C"). Basically I would put a new tee about 4" below the current drain line, then go from the top of the tee (vent) to the current drain (at "A"). Below the kitchen is unfinished basement, the drain is accessible but I would need to drill through two joists.

The only problem I see would be from "A" to the current vent and from "C" to the current vent would both be vents. I'm not sure that having both of those technically as vents is a problem or not. If I just capped "A" and took the drain to "C", I think I would possibly create venting issues. Thoughts?

If I use "A" as a vent, I think I would basically have this setup except the vent would split near "vent" and would have a second leg that went straight to "drain":
sink_dw.jpg
 

Cwhyu2

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You cannot use A for a vent, vent cannot go horizontal untill 6" above the flood level rim of the fixture it is serving or 42" AFF.
The best solution is to cut out the old tee and waste arm and install a tee and waste arm lower on the exsisting waste and vent.
Yes you will have to drill some studs and such but is by far your simplest solution.
 

Reach4

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How about
  • cap A, and keep the horizontal line as a cleanout. Now the path thru the existing santee can be a vent.
  • Add a new santee under the current santee. Santee would have a trap adapter poking out of the wall at, or near, the santee.
  • Run the trap arm from the disposal+sink drain stuff to the new santee under the sink, rather than having the trap arm go through the stud? No stud drilling.
Or if you are very tall people, put in a higher counter.:rolleyes:
 

Terry

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If you can run below and bring a pipe up into the cabinet, then use an AAV for the venting.
I see that being done a lot here on the West Coast.
 

Mike__B

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Well, I can't remove the cabinets, and with the drywall and further compromising the studs - its not a solution, nor simple. I could cap A and then just to a vertical drain at B through the floor. The vent for this would be approximately 52" away at C, and it is below the weir. AAVs are not permitted here. The tee is behind the dishwasher, so I can't just go right to the tee.

So I don't think I have a solution that meets code, regardless.
 
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