cylinder modification

I have two leluv clear cylinders I want to modify. I want to cut the flared end off the 2” and glue it to the flared end of the 2.25” one to keep my ball bag from sucking in. I pack the 2” too early so I moved to the 2.25” but said problem happens. These are thick (mold injected?) cylinders so I need to know if someone can tell me the right glue to use. I use it for water pumping so I guess I would need a water proof glue.

I highly doubt glue will work/hold up for very long. You said you pack the entire 2” tube? Have you tried pumping in stages? Aka filling the 2” then move onto the 2.25”?