Shocking: Why bleach and not chlorine sticks


May 30, 2013
It may be here somewhere, but can someone explain why it is best to use bleach instead of chlorine tabs to shock or increase FC in a SWG pool? How much bleach and what kind? In understand the SWG's role in slowly raising or maintaining FC, but how does bleach work over chlorine tabs when one needs to shock, due to algae, etc.?


Mod Squad
TFP Expert
LifeTime Supporter
Apr 17, 2010
East Texas
Speed to raise and the ability to HOLD shock level without any other additives you don't need....calcium, cya. Plain simple odorless bleach.


LifeTime Supporter
Apr 27, 2013
Central Massachusetts
Tabs and sticks take time to dissolve and they also contain CYA. To shock you want to bring up your FC immediately and most the time you want to avoid adding CYA. Simple liquid bleach/chlorine is the best (but can be a pain to transport compared to the other options).


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
Chlorine tablets/sticks are generally made out of trichlor. Trichlor adds chlorine (good), CYA (usually bad), and lowers PH (often annoying). They also dissolve too slowly to be used when shocking.

Bleach/liquid chlorine "dissolves" instantly, since it is already a liquid, and doesn't add anything that you don't want to the pool. It is also one of the least expensive forms of chlorine.


TFP Expert
LifeTime Supporter
Mar 1, 2012
North Georgia
Bleach is chlorine, just in liquid form without the additives that chlorine tabs have in them. Chlorine tabs require either CYA or Calcium to bind with the chlorine. We advocate using bleach/liquid chlorine because it only adds Chlorine to the water. If you use the tabs you are constantly adding CYA or Calcium, which builds up over time in your pool leading eventually to water replacement.


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
The solid forms of chlorine add either cyanuric acid, calcium, or lithium to the water.

High CYA renders FC ineffective and algae can flourish. If you've read any of the green pool threads, you'll find that most begin with high CYA levels. Dichlor and Trichlor also lower pH tremendously. Calcium buildup leads to scaling. The Lithium stuff is mega expensive. And before you ask - it's not possible to make a stable solid chlorine compound without these unwanted byproducts. If someone could, they'd be a billionaire.