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KJH-texas · Jan 16, 2009, 10:13 PM

I want to add a sink drain from and adjacent room to an existing laundry room. The original drain design does not physically allow space for another connection to the stack below the existing washer drain (see original below). I am thinking of modifying the washer P-trap and using the existing drain connection for the new sink drain (see proposed). Is the wet stack arrangement acceptable or do I need a vent on the sink drain?

Original:

Proposed:

Photo of original:

Thanks for any help... Kurt

Milo Dolezal · Jan 16, 2009, 10:17 PM

You can use Cross Sanitary Tee to get two drain inlets with single vent.

KJH-texas · Jan 16, 2009, 10:24 PM

Here are the attachmens

Milo Dolezal · Jan 16, 2009, 10:28 PM

It this project to be inspected ? Do you have Permits ?

KJH-texas · Jan 16, 2009, 10:34 PM

I have not started the reconfiguration yet, but was planning to have it inspected.

Milo Dolezal · Jan 16, 2009, 10:55 PM

If your job is being inspected, than you will probably have to put washer hook up to the left of the drain and run 2" pipe towards the sink. This horizontal run should not be longer than 48" to avoid venting it - or, if allowed in your area, use AAV. You will use double (cross) sanitary T to connect washer and sink drains together.

massplumber2008 · Jan 17, 2009, 06:44 AM

Hi Guys:

Kurt... One thought that came to my mind is to pipe this up as you drew it up (except use sanitary tees and add a full size cleanout) except that you will need to run an 1.5" vent for the sink up the stud bay (at the sink) and connect it back into the existing vent in the ATTIC.

See my picture below:

I have you piping this so you use SANITARY TEE fittings (no wye fittings off the vertical pipe in this case.. OK?). I would run 1.5" over to the sink but you will need to use a long sweep elbow to turn the corner (see note)... no restrictions on distance as this sink will have its own vent. Add a full size 2" dandy cleanout above the tee fittings (see note) as this is probably going to be required by the inspector... ;)

Finally, you would need to move that washer box up as high as possible as most states require a 30" minimum standpipe out of the washing machine PTRAP.

And just FYI... you cannot wet vent using a washing machine (or a kitchen sink)... that is why you must pipe this either as MILO suggested or as I have drawn below... :)

Let us know what you think on this...

MARK

Milo Dolezal · Jan 17, 2009, 08:49 AM

You are tight on space, especially with those cabinets being so low. Your stand pipe is already 23% shorter than it should be to begin with. If you add another San T bellow existing one, you will lower your stand pipe by another 6". Also, you are on slab so you have no luxury connecting easily bellow the floor. Of course, this option can be utilized if you elect to cut and break concrete floor.

So I would like to mention one more option you have: Eliminate existing washer drain and use it for sink instead. Drain washing machine into the sink. Pros: least work required to convert. Cons: Hose hanging over the edge of the sink.

massplumber2008 · Jan 17, 2009, 09:04 AM

That's probably his best bet overall, Milo! Cheapest, fastest and meets all code requirements. Nice... :)

Kurt, this is reasonable enough, but check to see what height the standpipe needs to be coming out of the ptrap and into the washing machine box in your area by asking the local plumbing inspector. In my area it needs to be between 18" and 30". If this is the case in your area then you should be fine as I posted at my earlier post!

Don't forget... there is an extra 1.5" of pipe at the floor inside the 2"x4" stud plate. If you cut out the plate around the 45s there now you can cut under the 45s and join onto the pipe there... ;)

Let us know what you find!

MARK