Getting new counter tops and want to get under mount sink. The problem is the old sink has 7 & 3/4in from the lip to the bottom of the sink. 9 & 3/4 from the lip to where the threaded part for attaching the P trap. When putting in under mount sink this will lower the drain etc. Where the P trap etc. ties into the wall is old cast pipe that runs inside the wall a bit till it reaches the stack. To change the cast pipe in the wall would involve a lot of demo and effort. I had a thought when writing this about capping off cast drain and run a new PVC drain inside the cabinet to the stack and then tie in the new drain. It doable as the cupboard beside the sink cupboard is a corner cupboard and open. If this is acceptable then that leaves how to tie in the new pipe into the old cast stack?

I replaced my in-law's toilet last night. I had to set the toilet twice. The first time I set it, I used this wax ring [url=https://www.lowes.com/pd/Oatey-Johni-Ring-Jumbo-Wax-3-in-in-Toilet-Wax-Ring-with-Sleeve-For-Hercules/3956161]Oatey Johni-Ring Jumbo Wax 3-in Toilet Wax Ring with Sleeve for Universal in the Toilet Wax Rings & Floor Seals department at Lowes.com[/url] and a standard wax ring stacked on top. The toilet sits on a thick tile and the flange is set slightly below the subfloor. After placing the toilet, the bolts were too short. So, I ran to Lowe's and bought long bolts and picked up 2 more jumbo wax rings and a standard was ring (wasn't sure what combo I was going to use). When I returned to pull the toilet to install the new bolts and wax rings, I saw the bottom was ring was not seated very well on the flange. I decided to use 2 jumbo rings for the second installation. This was late in the evening and I didn't have any other options at the time. I know I can get a flange extender and if that's what I should do, I'll pull the toilet again. However, is there anything wrong with stacking these 2 jumbo wax rings. I have read where some say never stack the rings and some that say it's okay. The rings I used, I would assume, would be safer since there's a sleeve with this ring. I have no clue what was originally used when installed. I have used these jumbo wax rings myself and they have always been enough and I can always feel the wax squishing down. When I did the first install, I didn't get a good feel of the wax squishing down (with the jumbo and standard wax rings). Using the 2 jumbos, I got a nice squish. I flushed the toiled several times and nothing leaked. That doesn't mean there's nothing leaking between tiles and subfloor.