[Latitude 28]

We replaced our rear toilet with a SANI-FLUSH macerating toilet and the mid bath toilet with a Dometic Gravity flush toilet.  The aft toilet works great.....but the front gravity toilet does not flush all that hot given the original piping is 1 1/2" ABS.  I wanted to increase the piping to 2" but the thought of removing the black tank to drill out the original 2 5/8" hole to 3" for the new 2" UNISEAL (https://www.amazon.com/dp/B072QR9KR6?psc...ct_details) was not on my list of things to do this summer.  So with some pondering, I came up with a method to increase the hole size while leaving the tank in place.  

I took a 2 5/8" hole saw (this is the bore guide for the 3" hole saw) threaded it on to the arbor of the 3" hole saw.  The thought of loosing a hole saw into the tank would mean pulling the tank anyway.  As a primary method of retaining the hole saw I put a 6" disk to keep it from falling into the tank.  A back-up, on the neck of the arbor there is an area that I twisted two separate pieces of wire in case I needed to retrieve the hole saw.  This neck area is smooth allowing the wire to stay stationary as the arbor rotates.  BTW the tank is empty and flushed in case I had to do the dreaded black tank dive. 

Now to rotate the hole saw in a restricted area....I do not have an angle drill and the ones available are too big to fit between the black tank and floor so I took a six point socket on an air ratchet that fit the arbor to spin the whole contraption.  Cutting the hole was a piece of cake and as predicted the hole saw did go into the tank but no further than the blue safety disk. 

The UNISEAL popped right in without any issues.  BTW the tank is empty and flushed.

Installing the pipe will be for another day perhaps tomorrow.