Washing Machine with Utility Sink - 1-1/2" Drain!

[Zhars]

I have an existing 1 1/2" copper drain that was used for the original utility sink. The washing machine discharged to the sink. I have recently started renovating the basement and added insulation to the exterior wall and am now about to finish the studs and plumbing. I know that the washing machine standpipe should be minimum 2". However if I install a 2" standpipe w/p-trap, I will not able to reduce to 1 1/2" as I get to the original copper drain in the floor. Is it possible to start with a 2" standpipe and then reduce it to 1-1/2" before the p-trap. Or it makes absolutely no difference and I might as well just go 1-1/2" all the way?

Attached (Laundry Plumbing) is a the layout I was going to go with. Also attached (Insulated Wall) shows the 1-1/2" copper drain and next to it is the 3" drain that is from the 2nd floor.

 

[Stuff]

Not a plumber but codes that I see don't permit any fitting that would reduce a drain pipe size. A 1 1/2" standpipe may be allowed by your local code but if at all possible you should go to 2" and tap into the 3" drain on the right. I've seen a washing machine overload an incorrectly installed standpipe - make sure you have a good floor drain.

Also - Do you have a vent pipe to tie in to?

 

[Sponsor]

 

[Reach4]

For function it might have an advantage:
https://terrylove.com/forums/index....for-s-trap-location-canada.36539/#post-259784

 

[Zhars]

Not a plumber but codes that I see don't permit any fitting that would reduce a drain pipe size. A 1 1/2" standpipe may be allowed by your local code but if at all possible you should go to 2" and tap into the 3" drain on the right. I've seen a washing machine overload an incorrectly installed standpipe - make sure you have a good floor drain.

Also - Do you have a vent pipe to tie in to?

Yes that's why I'm having this dilemma regarding the size reduction to 1 1/2". I suppose I could reduce it on the vertical standpipe section just before the p-trap just like Terry mentioned.

Regarding the 3" drain on the right. It is used by the 2nd floor bathroom so not sure if I'm allowed to tap into it. I would be adding the washing machine and utility sink to it.


Oh and I don't have a vent either! As there is no way Ill be going through 2 floors to the roof, I need to use an AAV which I heard does nothing for washing machines. At least it will help the utility sink.