Due to space constraints, I am planning to install 1 1/2 inch pvc piping through cabinetry to the sink tailpiece (with some type of tee) which will go straight down to the p-trap to the main kitchen drain. I have a poor ASCII diagram that describes the current thoughts. The V in the diagram is the opening where I will insert the drain hose from the washer. The height of 12 ft horizontal piping can only be adjusted about ±6 inches. Now assuming I do not run the kitchen sink while washing clothes, should this setup effective drain a load from a washer cycle.

| 12 inches
|              12 ft
                              |              |
                              |         exit |
                  18 inches   |              |
                              |   -----------|
                              \__/           |

I appreciate any thoughts. Thank you from a novice.

  • 2
    12' is way to far between a fixture and a trap. It's also to far for 1 1/2" pipe between trap and vent.
    – Tester101
    Jan 20, 2016 at 17:23
  • Have you thought about just putting a longer drain hose on the washer to a more accessible area? I don't remember reading anything in the plumbing code limiting the length of the washer drain hose.
    – ArchonOSX
    Jan 21, 2016 at 9:23

2 Answers 2


No Way on the tailpiece. It's got to be a full glued on PVC Wye (that accepts 2") above the sink trap or with it's own trap under there. Definitely go with 2" (not 1-1/2" pipe), but the 6"-ish pitch is fine.

Fill your sink up half way & drain it. If it squeals & has a very tight vortex smaller than your finger & the vortex starts & stops, then you need more vent air for an already starved drain.

You're either too far from the vent pipe or that pipe is too small & you'll need to put in an under-sink vent to avoid needing a utility sink that could hold the entire washer's dump that could then drain at a slower rate.


If your jurisdiction uses the International Plumbing Code or a derivative, there are several issues with this set-up.

First - 1002.1 would require the washer to have its own trap (none of the exceptions are applicable), and the trap needs to be within 30" of the standpipe:

1002.1 Fixture traps. Each plumbing fixture shall be separately trapped by a liquid-seal trap, except as otherwise permitted by this code. The vertical distance from the fixture outlet to the trap weir shall not exceed 24 inches (610 mm), and the horizontal distance shall not exceed 30 inches (610 mm) measured from the centerline of the fixture outlet to the centerline of the inlet of the trap.

Second - 709.1 (see linked table) and 406.2 require that residential clothes washers have a 2" trap:

406.2 Waste connection. The waste from an automatic clothes washer shall discharge through an air break into a standpipe in accordance with Section 802.4 or into a laundry sink. The trap and fixture drain for an automatic clothes washer standpipe shall be not less than 2 inches (51 mm) in diameter.

Third - Even assuming that you were putting in a 2" trap for the washer per 1002.1, 909.1 and 909.2 would require that the vent be within 8' of the washer's trap (which per the above has to be within 30" of the washer for a maximum of 10',6" from standpipe to vent stack):

909.2 Venting of fixture drains. The total fall in a fixture drain due to pipe slope shall not exceed the diameter of the fixture drain, nor shall the vent connection to a fixture drain, except for water closets, be below the weir of the trap.

If you can't vent the washer (and assuming the sink drains into a 3" stack), you could wye into the main stack and run a 3" drain instead of 1½", but I'd guess that isn't as practical.

If the drain is accessible below the kitchen, you'd likely be better off running a separate 2" vent for the washer (either re-venting it above or running it all the way outside by itself) and then branching into the drain below the kitchen. If you have the access, this would probably be easier than trying to run 12' of pipe through cabinetry.

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