If you are planning to use them as a weight-loss aid, please don't. I don't know THAT much about them except that it IS possible to get "addicted" to them. My mother was anorexic for 15 years, and reached a point where she felt she "couldn't survive" without her water pills. Goodness knows the effect all those years of the stuff had on her body -- but it can't be good. I also saw a program (on the Discovery Channel possibly?) about a woman who was so addicted to water pills, she had to enter REHAB. Which was bizarre...
My theory is that if you're bloated, there's a reason. Everyone gets bloated now and then, and your body is perfectly designed to work everything out for you without outside "help." I suspect diuretics really mess up the normal functioning of your anti-diuretic and diuretic hormones, which CAN'T be good, and who the heck knows what they do to your electrolyte balance, etc. Again, your body knows just what it needs (and doesn't need) as far as water goes, and in my opinion, your body should basically be left alone to do what it does naturally. Just my opinion, though.
I actually have no idea what purpose they're supposed to serve...meaning, what "medical" condition -- if any -- they're meant to treat. I just know I've heard really-not-good things about them.
Plus, if you lose weight on diuretics, OBVIOUSLY it's just water-weight you will lose -- which isn't the real goal, right?
Having said all that, if your doctor prescribes them for a medical reason, then of course you should take them.
Hopefully someone more knowledgable will post after me, as I doubt this response was very helpful.