PVC DWV pipe questions.....

I purchased a two family home, and each unit has its own washer/dryer hookup.
In the basement, I can see that one washer/dryer drain pipe is 2" while the other is 1.5".
Generally speaking, is either size "to code"?
I also noticed that both drain pipes are NOT sloped properly. In fact the 2" pipe slopes down 2", then back up 2" over a 20 foot run, and it will not be easy to fix (other utilities are in the way), but the drain seems to work fine and does not leak.
How critial is it that I have this sloping problem fixed?
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john snipped-for-privacy@hotmail.com wrote:

2" size for washer drain. That said, 1 1/2" PVC has very little restriction (unlike galv iron) and will probably work fine.
If the "hump" in the 2" drain doesn't give problems, leave it alone.
Jim
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