As per my earlier post i'm re-doing the sink drain to use the proper fittings, I've also decided to vent into the main house vent and just wondering what my options are in this scenario. (see picture) The white PVC you see is the new drain, the galvanized pipe in the corner is drain/vent for a bathroom fixture and the black cast iron is the main vent stack going out of the roof. I'm a little worried to cut the jack/king stud for the window and the corner studs as I would be weakening the framing of load bearing walls. Any suggestions how to best route the pipe? Out through the attic, or connect into the one of the vents in the picture?

EDIT: by the way even though I'm close to the drain in that walls I'm connecting to an entirely new branch that is vented but the vent is located roughly 20 feet away.





Edited 1 times.

The vent coming off the kitchen sink drain can't go horizontal until it's at least 6" above the countertop height. How high is the new window sill? A vent pipe rising at no more than 45* from vertical is considered vertical, so if you can't go up 6" above the countertop height, a vent angled into the stud bay next to the window would work, but then you have a larger oval hole in the framing. Does the drain have to come through the floor where you have it, or could it be moved to the stud bay next to the window? If you can move the drain, bring it up in the bay next to the window, install a sanitary tee and run an 1½" trap arm horizontally through the studs. 90* the trap arm into the sink cabinet and come out of the top of the sanitary tee for the 1½" vent. Extend vent into attic and then 90* over to tee into existing vent.

Strange regarding the counter-top height measure, in either case I have the 6" needed, new window is 46" off the floor. I cannot move the drain closer in due to foundation underneath, however if I understood correctly I can re-route (in theory) under the house to the stud bay on the right of the window and do what you suggest... but since I have the 6" needed I guess I don't need to do this.

Question about connecting to the existing vent in the attic, is it okay to cut the cast iron pipe and use a rubber pipe coupling to achieve that? or is there a better way?



Edited 1 times.

Yes, cut the cast iron pipe and insert a tee, using shielded couplings.

got it! Thank you Steve

you can change the cast iron elbow in the side wall for a tee. then if you can get that 1 1/2 over to the sink for a vent without destroying the house framing, that will work as a kitchen vent.

A possibility would be to actually dodge the corner and bring the pipe out of the wall next to the corner. When the countertops and cabinets are being put in, a small piece of 1/4"plywood can be used to hide the pipe. Set it at a 45 degree angle in the back corner from cabinets to countertop and treat it like the rest of the backsplash. When you are done it won't look out of place. It is really no different than what you do with whirlpool tubs to hide the access but still keep it accessible.

"The vent coming off the kitchen sink drain can't go horizontal until it's at least 6" above the counter top height."

Actually the normal wording of the codes are 6" above the flood level of the rim of the fixture (not to be confused with an over flow)

As long as the vent line is above fixture most inspectors will not give you a hard time

The reasoning being if the vent is below the flood level rim it can act as a waste line. If this was the case the fixture would have water standing in it.

If the existing horizontal vent at least 45" high Consider cutting out the CI Elbow at the existing vent. Cut at least 6" of pipe out with the elbow so cut 7 1/2" from center of the elbow. Then use 1 1/2" PVc to replace the elbow with a tee with 1 1/2" bands as shown above. If you are worried about the integrity of the corner studs and the king stud for the window, you can alway add a stud nailed into the worry studs for extra strength. Also you may consider nailing in 1/8" thick steel straps over those weak spots in the studs. If you have enough heighth for the horizontal vent then this will keep all the piping inside the walls. All the best.

Thanks for all the help folks. this is what I ended up going with..





Edited 1 times.