Vent into chimney for Hot water heater

We had dome work done on the house a couple years ago and the GC never got final plumbing inspections done. They had put in a larger (taller) water heater and routed it into the existing vent into the chimney, but that vent run has a slight negative pitch/flat to it now and it needs to be changed.

The fix is to move the vent into the chimney up higher to create a positive pitch. I want to do this myself and before I disassemble what is there I was hoping to have a couple questions answered.

What is typically used to sleeve the vent hole?

If i break a new hole through the masonry higher up, what should I use to seal around whatever sleeve I use there. (maybe I can use whatver sleeve is currently in the existing hole)

How should I patch (material?) the existing hole?

Thank you for any insights

bump...hoping to get some response to this

vent

The fly in your ointment could be if they have a clay pipe liner, which is something YOU could probably not make a hole in without cracking it.

Hi DrBob,
I can't testify to a typical material used to sleeve the hole but my preference is stainless because of the chemicals in the concrete patch material tend to corrode galvanized over time.
Patching the old hole and sealing the new pipe can be done with; http://www.rockite.com/ Both of these set up fast, expand to fill gaps and you won't have to worry about leaks.