Clean out cover would have been my guess also. Is it directly below where the drain is?
If that's a clean out cover, I want one.
It would appear to be a clean out cover?
and it's about 12 (that's approx 30.5cm for our Canadian brethren above lol) to the right of where the drain is.
Don't be offended I lived in Calgary for a few years so I'm almost part Canuck
Just your average 24 year old
We only use metric when we have to. I would open the wall around the clean out so the plumbers can give instuctions.
So here is what we've learned
Oh and there has been a change of plans.
My wife told me I wanted the sink in the laundry room in the corner shown instead of in the garage so I just have to get to the corner with the sink now instead of through a wall. Funny how being married changes things. lol
I assume 2" drain all the way into the slab?
Can't see it in the picture...
Yes on the drain.
So at this point it looks pretty straight forward to T into the PEX line, but I'm not sure about the drain and the vent, or even if a vent is necessary.
A vent is always necessary.
At this point you should check your locally used plumbing code to make sure that a 2nd fixture can be added on a 2" washer drain.
Are you looking at adding the sink to the right or, left of the washer?
How far over?