Nope, not good... way too many parasites available there...
Not saying you don't keep it clean, but stuff 'grows' in the tanks over the years...
Shove him in, toss in some soap, slam the lid, and flush. Presto--clean cat!
That was my thought as well!
He is getting big, though.
He is making the inspection tour
"found" water is always better than given water.