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.

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.

 

[Plumber1979]

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.

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.

First i would like to ask why this was done in PVC? If this is in a house it could have been done in ABS. What type of sink are you putting in? I was told by many inspectors that are former plumbers that if the standpipe is part of the sink drain depending on the size of the sink the standpipe can be 1 1/2" because the sink will act like a reservoir and because you are going into existing its not a big deal to stay 1 1/2 all the way. Unless you want to break up the floor a go 2" all the way.