standing drain pipe size requirements

duhFooLOctober 7, 2012

my new WM only opens from right to left, forcing me to place it further from the old drain pipe.

I've read everywhere that current code requires a 2" drain pipe.

from out of the wall, I see 1.5" pipe.

since it is covered wity drywall, i can't see much more.

My father says the code should be for the main drain pipe and that 1.5" is okay with the vertical riser and the horizontal pipe leading into the wall drain.

is he correct or do i need to break the wall and change it to a 2" pipe?

what if the pipe inside is also 1.5, do i need to replace the whole drain assembly?

is it possible for me to use a 2" pipe and use an adapter to connect to the 1.5 in the wall, in case the inspector insists on a 2" pipe?

house was built in 1965.

he also mentioned that as long as the vertical stack was above the WM tub, there should be enough pressure to drain properly with a 1.5" pipe.


first time homeowner here.

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one more addition. i am going by california plumbing code.
I was not able to find city/County specific codes.

    Bookmark   October 7, 2012 at 1:15PM
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If you don't touch it, then it's fine at the current 1 1/2" that currently exists. Just buy a longer drain hose. If you start redoing stuff, then yes, you've got to open up the wall and make it all 2" to the main drain, which will also mean opening up the floor for access to change that portion of the piping as well.

    Bookmark   October 7, 2012 at 1:50PM
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is it possible to extend the drain hose 4-5 feet?
do i hook it up high enough so that the extension slopes down to the original drain?

    Bookmark   October 7, 2012 at 2:23PM
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