The only time I use a water flush is with a clogged pipe. I'll take an eye dropper and drip in very hot water into the bowl. Let it sit about 2 minutes and then work on the clog from both ends with a straightened paperclip, (an indispensable pipe tool), and/or a shank brush. Usually does the trick, though for more stubborn clogs sometimes I do the same routine very carefully with rubbing alcohol. Very rarely both. That, of course, is only for clogged bowls. Never have attempted it with stems but, then, haven't had any clogged stems I couldn't resolve with a pipe cleaner only.