There are some that get around Chem Geek's problem by actually encapsulating the Cal-Hypo in plastic, which, when empty, you must discard. I believe PoolLife may still make them but HTH only makes the tablets, which are horrible. They are supposed to last 5-7 days but I found, in my skimmer, they dissolved in less than 12 hours, and into a skimmer clogging wet cement. I will NEVER use them again.