Diuretics, or water tablets such as furosemide, bumetanide or the weaker agent bendroflumethazide, are used in:

Heart Failure: these drugs clear the excess  fluid from your body

Hypertension: bendroflumethazide and Indapamide appear to reduce blood pressure

Some of these drugs can cause side effects by leeching salts out of your body, making you feel week. They can impair kidney function if over used.