wet venting question

Mechanics shop in Southern California, must be to code. is it possible?

I want to add a sink to a room that only has a toilet. the sink will be wall hung with cold water only. The toilet drain is stacked underground ,4x3 cast iron closet bend goes back to a 3" sanitary tee and drops to a sweep and then runs horizontal. out of the top of that 3" cast iron san tee is a 2" galvanized vent that goes through the roof, I want to cut into that galvanized vent with a 2x 1 1/2 T and arm over 3', then turn out for my lavatory.

cut out a section of vent and use 2x 1 1/2" galvanized tee with sections of pipe on both 2" ends and no hub that into place, 3' (+/-) 1 1/2" arm over with a 1 1/2" galvanized 90 tuning out, with a nipple in that.

cut out section of vent and band in 2x 1 1/2" cast iron san tee, with 1 1/2" cast iron arm and a quarter bend turning out.

what would be ther proper way to do this if there is one. Thanks guys.

As a general rule, the only time I will use metallic drain pipe is when the pipe is located in a return air plenum. In your situation, I would use a plastic DWV sanitary tee, with a short section in top and bottom, and no hub band that into the vent.

I don't know California code, but in my area what you want to do would meet code requirements. Hopefully Mr. David will see this thread and comment.

Here's the Calif Code reference to wet venting. Hand sink requires 1-1/2" drain and the toilet vent is 2" so the vertical drop between the sink and toilet is the wet vent.

908.1 Vertical Wet Venting.

908.1.1 Where Permitted. Wet venting is limited to vertical drainage piping receiving the discharge from the trap arm of one (1) and two (2) fixture unit fixtures that also serves as a vent not exceeding four (4) fixtures. Wet-vented fixtures shall be within the same story; provided, further, that fixtures with a continuous vent discharging into a wet vent shall be within the same story as the wet-vented fixtures. No wet vent shall exceed six (6) feet (1,829 mm) in developed length.


908.1.2 Size. The vertical piping between any two (2) consecutive inlet levels shall be considered a wet-vented section. Each wet-vented section shall be not less than one (1) pipe size exceeding the required minimum waste pipe size of the upper fixture or shall be one (1) pipe size exceeding the required minimum pipe size for the sum of the fixture units served by such wet-vented section, whichever is larger, but in no case less than two (2) inches (51 mm).


908.1.3 Vent Connection. Common vent sizing shall be the sum of the fixture units served but, in no case, smaller than the minimum vent pipe size required for any fixture served, or by Section 904.0.



California Plumbing Code

Okay so this would be allowed under California code.

keeping it all metal pipe, staying away from pvc or abs, what would you recommend, galvanized or cast iron, I have a pair of cast iron cutters. is there an 1 1/2" no hub by FIP 90 that I can screw a nipple into, or are there cast iron trap adapters, what would I use if I went cast iron. or since its steel, just go steel?

this dumby greatly appreciates your help.

Galvanized steel, and either run the entire trap arm in copper, or transition to copper with a male adapter into the galvanized 90 that turns out of the wall. You could use a cast iron tapped tee so that you wouldn't need the short nipple on either side of the galvy tee. 1 1/2" cast iron is not all that easy to find, and no hub arms are rather floppy, speaking from experience.

Unless you have to meet some fire code, plastic is your best choice.
use a 2" x 2" x 1-1/2" tapped NO HUB cast iron santee . plastic will give you better flow. if it has to be metal use DWV copper with a tubular brass p-trap