Just moved into a new house and the previous owners had their washing machine connected to a utility sink faucet and draining into the sink itself. I'm trying for a more permanent installation! My problem is, the more I search on how to correctly set up the drain, the more confused I seem to get.

I'd like to put the washer immediately to the left of the existing utility sink. The main drain stack for the whole house is to the right of the sink, in a rear corner of the house. The first difference I have from most threads I've been finding online is that I have 2 pipes running vertically instead of the one I usually see pictured. I believe these 2 are tied together at the basement floor, where a single 4" pipe runs under the floor to the main trap at the front of the basement.

What confuses me is that the 1.25" drain from the kitchen sink above connects to the 4" stack (as does the toilet, sink, & tub in the bathroom above that), while the 1.25" drain from the basement utility sinks connects to the smaller 2" vertical pipe (don't see anything else that connects to the smaller pipe above).

So where is the best (and hopefully easiest!) place to connect a washer stand pipe that will be 8' from the stack(s)? And does it need to be vented? And if so, what is the best way to vent it given this arrangement?

Here is a picture of how it currently sits for visual reference:




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Your picture did not come through and there is no way to answer your question without it, because you pipe description is too erratic.

Upsize the laundry sink drain to 2" and include the washer on it. The vent can be installed thru the basement wall near ceiling height to the exterior.

Strange; the picture was loading for me fine. I edited my original post to switch to a different image host anyway.

you can use a AAV (studor vent) to make venting easy.

Before you change anything, you need to get a plumber out there to see what is going on. That looks like someone tapped into the vent line for a set of whole house traps to add that sink. If that is the case, you need to make sure you have access to clean the line out in case of backup. You would probably be better served to remove the whole house trap and change the area over to plastic and install a cleanout while you have the new washer/laundry sink drain installed.

the 2" vertical u see connects to the stack below grade, the vertical part going up is the vent for the sinks

the sinks ARE vented properly


consider simply redoing what you have way over to the right as you have a good, but old, setup


IMO: 'hard venting' is ALWAYS preferable to AAV

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

There is no way that vent could be connected to a "house trap".

my terminology may be misleading, but, the 2" would be a 'vent stack'

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

The trap for the whole house is at the opposite end of the basement from this stack. Waste traveling down this stack (at the rear of the house) then runs under the basement floor the length of the house, through the main trap at the front of the basement, then from there out to the street.

So, can I replace the sink drain 1.25" plumbing with 2" while adding a standpipe for the washer and still have proper venting as it's set up now? Or would adding the standpipe necessitate a change to the vent arrangment?

Thanks for the help so far.



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Because the washer drain (trap arm) will be in excess of 8' from its connection point, the washer drain will need an individual vent, either a piped vent or as some have suggested, an AAV. The drain size needs to be 2". The laundry sink can be connected via a sanitary tee to the washer standpipe.

quote; The laundry sink can be connected via a sanitary tee to the washer standpipe.

Not around here it wouldn't. and since the washer trap would have to be above the sink connection, AND because of the sink arm's length, it would need an intermediate vent connectinb back to the existing one and the washer trap woudl connect above the sink connection.

Why not just dump it into the new laundry tub and be done with it?