I bought a house where the owner paid a plumber to convert the bathroom into a laundry room. My wife would like the bathroom restored so I am moving the stackable laundry to an adjacent closet, reinstalling a vanity and sink and toilet. The plumber did not install a separate vent for the 2” laundry instead using the dry vent associated with the back to back separate bathroom sinks. I have added a dedicated vent for the about to be moved laundry My question is can I add the new sink drain to the 2” vent which is 4” away from the drain? Will the laundry empty my 1 1/2” sink p trap? Or should I stack a sanitary trap above the clean out on the drain? I believe I cannot wet vent the laundry trap by code, but in this situation, the amount of air has more than doubled than what was professionally installed and everything worked fine. Ideally I wanted to install a double fixture for the sinks, but I am really tight on available ABS to bond to and I am unable to find needed 2 x 1 1/2” x 1 1/2” x 1 1/2” double fixture. Picture shows old laundry box and copper in original location. ABS is not glued. New 2" vent on left with Sanit with combo to drain in center. Single story on slab.
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Is "A" the new laundry drain and "B" is where you want to install a tee for lav sink? According to the CA Plumbing Code, a lavatory sink is rated as 1 fixture unit and able to drain into an 1 1/4" pipe. The wet vented section needs to be at least 1 pipe size larger than what's required for the lavaotory drain and a minimum of 2", so your 2" pipe diameter covers that requirement. All fixtures involved in the wet vent need to be on the same floor, you have that covered. I see nothing in the code stating that a clothes washer can't be wet vented. If you're concerned with siphoning, add an 1 1/2" vent to the washer drain and tie it back into the stack, 6" above the flood level of the lavatory. 703 and 908 are the chapter sections in the 2025 CA plumbing code that discusses pipe sizing and wet venting. There's a thumbnail diagram in the UpCodes' version of CA plumbing code(908.1), that shows a washer standpipe being wet vented by a utility sink, but you need to be paying subscriber to enlarge the diagram.

Yes. You are correct regarding A & B. I will add an additional dry vent as you suggested. Great help. Thank you.



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