Two Questions, Same Project:
1) I have remodelled our kitchen, moving the kitchen sink to the other side of the room, so the existing vent is not accessible at the normal location in the kitchen cabinet just after, but above the P trap. Fortunately, I have a full basement below, and can easily run the existing vent down and around from its original location to just underneath the new sink area, just below the first floor joists, maintaining a constant 1/4" per foot or better downslope from where the vent rises vertically to join the stack up in the attic. So that the vent drops down continuously from its connection in the attic to its connection above the trap (to say it the other way round, the vent goes up from its connection above the trap all the way up to the attic...

I was wondering if I could just drop the sink drain straight down through the floor, put the P-trap in the basement just below the floor joists in such a way that after the trap the vent would join above, while the drain would slope down 1/4" per foot or so to the main drain. The drain run to the main drain is about 12 feet, so I know that I should increase the trap and drain size from 1-1/2 to 2", and that I should also add another vent at the 6 foot point.

I just was not sure about dropping the drain straight down to the trap in the basement - would I still need a trap in the kitchen sink cabinet? - (without a vent at that level I don't see what good a trap in the cabinet would do). I live in Massachusetts, so an AirAdmittanceValve is not legal.

2) Before I start cutting, I thought I would ask some advice.

I am needing to add a new kitchen sink drain connection to existing vertical stack. It occurred to me that I will need to cut the stack an appropriate length to fit the new drain tee properly, which is a shorter length than the tee's
End-to-end length.

My question is - with an existing stack which already has a number of inaccessible connections in upper level walls, and is rigidly connected to the main drain below, how would I temporarily spread the gap where I made my cut, so that I can fit the new tee and then quickly pull the gap back together again before the solvent/glue sets?

Would a flexible strap connector be the way to go, and is it legal?

Speedball1 will read this later today and give you the best advice. All drains need traps and venting. Your S trap is as much out of code (legal) as you air admittance valve (Studor) so you are boxing yourself into a situation. Drains go down but I never direct a vent down. Speedball may save your remodeling dilema. He will also tell you which hubless collars will help rejoint your stack.

"I was wondering if I could just drop the sink drain straight down through the floor, put the P-trap (S-trap?) in the basement just below the floor joists in such a way that after the trap the vent would join above, while the drain would slope down 1/4" per foot or so to the main drain. The drain run to the main drain is about 12 feet, so I know that I should increase the trap and drain size from 1-1/2 to 2", and that I should also add another vent at the 6 foot point.
I just was not sure about dropping the drain straight down to the trap in the basement - would I still need a trap in the kitchen sink cabinet? - (without a vent at that level I dont see what good a trap in the cabinet would do). I live in Massachusetts, so an AirAdmittanceValve is not legal."

Yeah you could do that. Drop straight down to a 2" trap under the fl.oor. Make it low enough to run a vent horizontally off a fitting that's rolled up on a 45 degree angle with a street 45 coming off the branch of the fittinbg to pick up the horizontal vent line. Only one trap to a fixture so you won't need one in the cabinet and you won't need to add a vent 6 foot on down the line since you have already vented the sink once.

"My question is - with an existing stack which already has a number of inaccessible connections in upper level walls, and is rigidly connected to the main drain below, how would I temporarily spread the gap where I made my cut, so that I can fit the new tee and then quickly pull the gap back together again before the solvent/glue sets?"
Would a flexible strap connector be the way to go, and is it legal?


I don't know about code in your area, (will this job be permitted and inspected?) but sometimes No-Hub Couplings,(see image) are the only thing that will work. Don't forgetto secure the vertical stack before you make your cuts. Good luck, Tom