I also know that raising and lowering chlorine has an opposite effect on pH reading.
Lifted from the Ph Wiki :
What is the Effect of Adding Liquid Chlorine on pH?[edit]
It is a myth that liquid chlorine will raise pH. The myth is based on a misunderstanding of chlorine chemistry.
Adding liquid chlorine to water can cause a temporary increase in pH which is usually offset by the chlorine reacting with organics and biological matter which are acidic (creates a proton) reactions. Thus, on balance, the net chlorine reactions are pH neutral.
[7]
Most retail and commercial liquid chlorine products contain a small excess of lye from the manufacturing process but this amount of OH- is minimal and does not change the pH with normal levels of liquid chlorine use.
If one were to add significant amounts of liquid chlorine (for example, raising the pool water chlorine concentration to SLAM FC levels), then the pH rise would need to be offset by an initial lower of the pH with acid. This is why TFP requires a pool owner to adjust their pH down to 7.2 prior to starting the
SLAM Process.
Adding liquid chlorine DOES increase the pH at first, however as it's used up the acid that's created lowers it back down to where it was before......thus equaling each other out making it pH neutral.
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