I currently have a washing machine and dryer in the basement and wish to move them both upstairs. I can tap into the same drain line, but it will be about 20' from the old p-trap. Should I install a new p-trap upstairs and take the old one out, or can I have 2 in the same line, or is the one in the basement sufficient?

Also there is no vent in the basement for this drain line just a p-trap and about 3' of pipe sticking up; will I need a vent now that I am moving it upstairs?

1 Answer 1


Ideally, you should move the P-trap upstairs, and vent through the roof. Under no circumstances should you have two p-traps in one line. You get an air-lock between the two, and funny stuff happens.

You want something like this: enter image description here

  • 1
    Awesome. I'd like to see Google Sketchup do that!
    – Kaz
    Apr 2, 2013 at 0:17

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