I would like to install a washing machine in my basement, about 30 feet from the main waste stack. The stack is fully accessible and already has a capped 2" port about 8" above the concrete floor.

Can this be done? How do I look up the diameter and slope requirements? Where do I put a vent?


1/4" per foot of slope is generally considered the minimum slope, so as long as you have a bit over 7" to work with vertically, you should be able to slope the drain over 30' just fine. You'd set up your discharge p-trap, and then vent immediately after that...tying that back to the main vent stack. So you'll end up with two 30' feet runs of pipe (drain + vent).

Obviously, check with local plumbing codes for specifics.

This all assumes you have water hookups in that location. If not, then you'll have to get those over there as well.


here is how you would do it in southern Ontario. The discharge line on a washing machine requirement is 1.5" pipe. The required slope is 1" drop in 8ft, but do yourself a favour and make it 1" in 4ft so you should be able to start at your existing 2" hub and go up 7" total for your run over the 30ft. Your connection should go something like this:

  1. Connection nipple for discharge line from washer, best to be vertical (up), but can be horizontal if need be

  2. Trap assembly and a cleanout port

  3. T-straight (not t-y) fitting with drain horizontal out and vent vertical up

  4. Drain line on downhill slope over to stack and into t-y (with the t-y) in the correct orientation (the water wants to always flow down, not up). you can tie this into your existing hub with a reducing coupling.

  5. Vent line on uphill slope over to stack to a new t-straight. you have to cut the stack t have enough removed from it so that you can insert the new t-straight with a couple of nipples attached. usually around 12" with 3" ABS DWV. then you slide a fernco (rubber coupling) or MJ style (mechanical/rubber) over the bottom of the original stack pipe and one over the top of the original (use dish soap to lube it up). then assemble all. tip - fit it all first, then glue it second.

  6. Support all pipes every 4 ft with grapple bar connected to whatever is behind it. if need be, run a 2x4 from floor to ceiling to attach the grapple.

  • 2
    I am down voting this answer because it is so bloody hard to read without proper formatting. If you can take the time to post a lengthy answer then add the small bit of effort to make it readable and look like it was written in a professional manner.
    – Michael Karas
    Nov 29 '15 at 18:56
  • oh no. my answer is being downvoted. does anyone have a hanky to wipe my tears? Nov 29 '15 at 19:14
  • 1
    there, now I have edited my question to make you happy. Please, if you can take the time to post a lengthy comment about my writing, then add the small bit of effort to please send me a Jamaican fruitcake for Christmas, and wrap it in a professional manner Nov 29 '15 at 19:22
  • No downvote from me since code varies by locality, but the requirement for washing machine discharge is 2" per international plumbing code (section 406). Dec 1 '15 at 0:23
  • 1
    Ah, another amateur plumbing expert who thinks that more slope is always better. Codes specify 1/16 to 1/8 inch per foot for some very practical reasons that will come back to bite you and anyone who follows your advice.
    – Ecnerwal
    Dec 1 '15 at 3:17

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