comments on new laundry config?

i have one 1.5" opening to run laundry drain into the base of kitchen sink stack. the question is should i drain the washer into the sink and the sink into a regular 1.5" drain -- OR -- can some sort of standpipe arrangement still work in this situation?

if i use 2" pipe narrowed to 1.5" between trap and 2" stack, and it doesn't work,would it just back up into the tub anyway? wouldn't that still be better than splashing the whole discharge into the tub?

there would be 2 feet between tub and stack, 3 feet between tub drain and stack, and four feet between washer outlet and standpipe (if i put the standpipe as close to stack as possible).

blue is cast iron and purple is pvc in this pic. i'm not interested in breaking into the floor or cutting into the cast iron stack for this.

many thanks for your comments. what would you do in this situation?

Stepping down the size of a drain pipe is alwas against code and always a bad idea. It is a worse idea for a washing machine.


Can't tell what you are proposing on that second pic as far as what that trap serves, etc. But the only thing that MIGHT work, is to have a deep laundry tub, drain the WM into that, and drain that sink through a trap into the 1½" arm from the kitchen sink. i don't see the whole picture on vents, but I am not sure if what you have will cut the mustard.

sorry... this is one picture of two floors. kitchen sink is upstairs immediately above basement laundry sink. i just wanted to show the whole of what this stack is used for. above kitchen, everything vents up to roof exactly as it should. this is 85-year old original work.

i can accept that stepping down is against code and always a bad idea. so that means i can't do a 2" standpipe.

is a 1.5" standpipe an equally bad idea, even if i connect the laundry tub to it above its trap?

i'm thinking that if the sink drained directly into the standpipe, sharing a trap, the any backup in the standpipe would rise into the sink, as long as the top of standpipe is above top of sink, it can't overflow?

so the main question is: is there any kind of 1.5" standpipe/tub drain arrangement possible that would be better than simply pumping the machine into the sink and draining through a proper 1.5" sink drain?

You might get away with 1.5" drain line on some older washing machines, but many of the newest ones pump faster, and water would backup in the line of a 1.5" line. Using a sink lets it act as a big buffer.

thanks, guys. i'm gonna make it spit into the sink. too bad they don't make bowl-shaped utility tubs with a hookup that would swirl it clean.