I just installed a new granite countertop and sinks in my master bath. The new sinks are lower than the old ones, causing the J trap to be about 1-2 inches lower. What do I do to fill the gap between the J trap and the P trap?

Review this post. This was a kitchen sink, but the problem is basically the same. Note the difference in the normal trap and what I found at Home Depot.

https://www.askmehelpdesk.com/plumbing/waste-disposal-pipe-back-pitched-178738.html

I just installed a new granite countertop and sinks in my master bath. The new sinks are lower than the old ones, causing the J trap to be about 1-2 inches lower. What do I do to fill the gap between the J trap and the P trap?
No problem! Since the bottom of the lavatory pop-up has a 4" tailpiece simply cut the tailpiece back and install the trap in the normal fashion. Good luck, Tom

OK, here is what I did. The lavatory assembly is a Pegasus (Home Depot). The stand pipe and pop-up assembly are a "new" design, with a large adjusting nut on the standpipe assembly, about 1" to 1-1/2". This drops the pop-up ball joint about the same amount. This did not allow me to be able to cut the standpipe back.:(

So, what I did was to use the old standpipe, trimming it back about 1-1/4". Everything went back together like a snap after that. The new assembly looks great. I used a little CLR to clean up the lime and soap scum on the old pop-up assemblies and they look like new. As they were Pegasus as well as the new ones, all the branding matches as well.

Jim:)

Congratulations! On working around the problem. Tom