kitchen drain

[jpiazza]

Hi all. I have a 2 inch drain going into the mainstack via a short run of about 1foot of 1 1/2 inch. There is a slop sink at the point where the pipe reduction is. Is there a problem with this drain backing up because of the restricted flow of the downsized pipe? The fitting on the stack is 1 1/2 threaded cast iron. Would it be best to open this up to 2 inch as close to the stack as possible? Thanks in advance.

 

[GrumpyPlumber]

Hi all. I have a 2 inch drain going into the mainstack via a short run of about 1foot of 1 1/2 inch. There is a slop sink at the point where the pipe reduction is. Is there a problem with this drain backing up because of the restricted flow of the downsized pipe? The fitting on the stack is 1 1/2 threaded cast iron. Would it be best to open this up to 2 inch as close to the stack as possible? Thanks in advance.

NEVER a good idea to decrease a drain size downstream.
A clog waiting to happen.
It would be better to run it 1-1/2" all the way, but your slop sink has a 2" drain....
The right way would be to cut in a 2" wye at the stack and vent between the trap and the stack.