Adding Washing Machine Standpipe in Basement

[John Bush]

Right now, my washing machine in the basement drains into one of those very old, super-heavy concrete utility sinks. The sink is starting to crack and leaking more often, it often clogs with the lint from the washer, and we're tired of switching out the mesh sock covers. I want to put in a standpipe for the washing machine to drain into and avoid the sink altogether.

Attached is a sketch I drew up that shows my drainage and venting system. The solid lines are the pipes I can see and know; the dashed lines are what I can't see, but I'm making an educated guess at. In red pencil, I've sketched out what I'm thinking for the standpipe, but want feedback on if this will work and if it's vented properly and that I won't have to worry about backup or overflow.

To summarize it, I want to cut into the copper drainpipe that runs from the kitchen sink upstairs, put in a PVC (or ABS?) sanitary t, run it to a p-trap, and then the standpipe. Is there anything else I need to do or think of?

THANK YOU!!

 

[Terry]

The washer needs it's own venting. The vent from the washer can ti into the laundry sink vent at 42" above the floor.
Without the washer being vented, the upstairs kitchen sink will be siphoning the trap.

You can't run water from the sink down the washer vent.

 

[Sponsor]

 

[John Bush]

The washer needs it's own venting. The vent from the washer can ti into the laundry sink vent at 42" above the floor.
Without the washer being vented, the upstairs kitchen sink will be siphoning the trap.

You can't run water from the sink down the washer vent.

Thanks so much, Terry - this really helps. I saw this diagram before, but was trying to best interpret it for my setup. Based on this, I mocked up two options to properly vent it. The red pencil is what would be new piping. Would you recommend Option A (tie into kitchen drain stack) or Option B (tie into Utility sink drain stack) below? My gut says option B so that I only need to cut into one pipe and can just put ABS in there. Thanks again - this place is a welcome wealth of knowledge!

 

[Terry]

They both work, but it may be easier to go with B. That way you're only cutting one stack.

 

[Reach4]

The vent split has to be at least 6 inchs above the rim of the sink and the top of the standpipe.

I suggest you add a cleanout for the path with the kitchen waste, since those tend to clog where the line turns from vertical to horizontal below the floor. The washer drainage would probably help to keep that clearer.

 

[Bob Schubert]

Would not option B cause the vent for the utility sink to be "Wet" in the current configuration?

 

[wwhitney]

Would not option B cause the vent for the utility sink to be "Wet" in the current configuration?

Yes, it would. Under the IPC (e.g. Michigan) the configuration shown would be allowed as an IPC911.3 common vent connected at different levels. The laundry standipe is 2 DFUs, so the pipe between the two san-tees only has to be 2". But there is the usual IPC 406.2 issue that below the laundry sink san-tee, the branch drain carrying both the laundry sink and the clothes washer needs to be 3". [The same is true in option A.)

https://up.codes/viewer/michigan/mi-plumbing-code-2015/chapter/9/vents#911.3

Under the UPC (e.g. Washington as in the OP), option B is not allowed as drawn. Vertical wet venting is limited to wet vents draining fixtures of 1 or 2 DFUs, and a washing machine standpipe is 3 DFUs. However, a laundry sink is only 2 DFUs, so if the laundry sink connects to the upper san-tee instead of the washing machine, that would be a UPC compliant wet vent. The pipe between the san-tees still only needs to be 2", as does the pipe below the lower san-tee.

https://up.codes/viewer/washington/upc-2018/chapter/9/vents#908.1

Cheers, Wayne