Lowering sink drain/installing disposal

[IndyDave]

Hi - we are replacing our kitchen sink with an undermount that is deeper. Based on the difference in depth, I will need to lower the outlet at the wall and have a few questions:
1) When I lower the sanitary tee (probably around 3-4 inches) am I ok to just use a Fernco connection above the tee to reconnect to the vent pipe?
2) When I connect the disposal does the discharge tube need to slope slightly away from the disposal (circled in a photo from another discussion on this site) -- I'm assuming it can't be perfectly flat? Same question for the pipe running from the p-trap to the sanitary tee.
3) Does the outlet tee fitting need a baffle (similar to the attached pic, again borrowed from this site)?
4) I have heard people recommend silicone instead of plumbers putty for the sink flange - thoughts?
Thanks in advance for your advice! Dave

 

[Jeff H Young]

1 fernco is a brand use the proper coupling with metal shield


2 yes water should flow away from disposal not just lay inside
3 with baffel
4 putty

 

[Sponsor]

 

[Reach4]

I'm assuming it can't be perfectly flat? Same question for the pipe running from the p-trap to the sanitary tee.

1/4 inch fall per foot is the magic number.

 

[Terry H]

What Jeff said for the band. The fernco the rubber one is too flimsy for that and the shielded ones just help stabilize a lot more. Either will work but it just fits the application better in my opinion.

 

[IndyDave]

Thanks all for the advice. Turns out it's a bit more complicated - the pipe in the wall runs horizontally rather than to a sanitary tee (goes through at least one stud) -pics attached. The dishwasher is directly beside it - is it likely that the tee is located behind the dishwasher? I can pull the dishwasher out but would have to continue cutting out drywall until I find it? Unfortunately it's an exterior wall so can't access from the other side. Any advice would be appreciated...thanks.

 

[Reach4]

Thanks all for the advice. Turns out it's a bit more complicated - the pipe in the wall runs horizontally rather than to a sanitary tee (goes through at least one stud) -pics attached.

Not unusual.

The dishwasher is directly beside it - is it likely that the tee is located behind the dishwasher? I can pull the dishwasher out but would have to continue cutting out drywall until I find it?

Take the trap off of the trap adapter. Run an electrical or plumbing snake in. You should feel when you hit the santee. Mark that distance on the snake, and you can figure where the santee is.

 

[Jeff H Young]

Not unusual.
Take the trap off of the trap adapter. Run an electrical or plumbing snake in. You should feel when you hit the santee. Mark that distance on the snake, and you can figure where the santee is.

Bingo I like that!

 

[Terry]

High high off the floor is the drain know. At 16" or lower a 10" deep sink should fit with a disposer.

 

[Jeff H Young]

If it needs lowering you gotta do it.

 

[IndyDave]

High high off the floor is the drain know. At 16" or lower a 10" deep sink should fit with a disposer.

Current drain is around 18 inches off the floor (at midpoint).