Why and When Do I need to "shock"?

[CarlD]

The shock you can buy at the pool stores supposedly rapidly disapates overnight so that the pool is ready to go the next day correct? So what should I use to shock and should I even bother doing it as long as the water is in balance and everything is clear.

Let your common sense guide you. The pool store stuff is HYPE. Once the "shock" dissolves, it puts chlorine into the water. Chlorine is chlorine is chlorine! There is NO difference in how fast it disapates once it's disolved into the water. Testing your chlorine levels is the best way to learn what to expect.

If your water is fine, shocking isn't necessary. You shock when your water isn't fine to prevent it getting worse.

[Rangeball]

Have you seen this thread?

http://www.poolforum.com/pf2/showthread.php?t=2200

[prh129]

In a nutshell, shocking means to raise the chlorine level high enough to cause a reaction that burns up bad stuff. The chlorine level needed to do this depends on your CYA level. Measuring CC (combined chlorine) is the way to determine of you have enough bad stuff in your pool to shock. Generally 0.5 or under is OK for CC, above that you can shock to bring CC down to 0.

Having a lot of people in the pool can cause CC to go up so it's a good idea to check after you have a lot of people in the pool. An FAS-DPD test is what you need to accurately measure CC. The OTO kit that tests chlorine and pH tests for total chlorine which is CC + FC (free chlorine) so there is no way to tell from the OTO result how much FC vs CC you have.

Peter