What's the correct laundry drain stack order?

Question

I am installing a new washer box. (see picture for reference) My plan was to switch out the Wye from the sink so the top was 2" and put the p-trap and Wye from the washer just above that in the stack. Then reattach the vent to that. My buddy was making a comment that a washer Wye has to go below the sink Wye in the stack.
As you can tell doing so would be a bit of a pain given the position of both appliances. I will say I'm not up to par on the plumbing codes (pretty sure he isn't either).
Is there any reason that I cant just fit in the washer above the sink Wye?
Location is Virginia.

Jeff Wheeler · Answer

You'll need to change the tee on the vertical pipe to a 2" tee for the laundry drain.  You're not allowed to reduce to a 1-1/2" for a few inches of horizontal branch and then increase to 2" again for the washer trap & standpipe.  However, the washer trap & standpipe does need to be minimum 2".
PEX crimp connectors certainly can be behind drywall.  Check with your AHJ if you have any doubts about your local rules, but these are reliable connections.
You are probably going to need to reroute the copper supply pipes to fit the laundry trap in that wall cavity.  Keep in mind there are several height restrictions on laundry standpipes.  It must be >= 18" above the trap weir and 30" to 48" above the floor.  The trap itself should be >= 12" above the floor.

What's the correct laundry drain stack order?

One Answer

Add your own answers!

Ask a Question