Trichlor effect on PH

[Wildcat]

When I go to pool math and enter 16 oz of trichlor it says the effect on PH will be .59.
Does that mean if my PH is 8.2 after the addition it will be just over 7.6?

Or does it mean .59 of .1 and my PH will only drop to like 8.1?

I added trichlor shock last week ( my CYA was actually down to 25 where it was close to 200 two years ago. Yea!) and it seemed to have little effect on PH

 

[Richard320]

The pH change estimation is at best an approximation. As it says immediately below Effects of Adding Chemicals

Note: pH calculations are not exact. These numbers are only suggestive of the relative magnitude of the pH change you can expect. Small changes, +-0.4, with pH between 7.2-7.8, TA around 80-120, and Borate near zero will be approximately correct. The further you go from those ranges the less these pH changes will correspond to reality.

pH is logarithmic, like the Richter scale. From 8 to 7 is 1/10 the change from 9 to 8. The higher the initial pH the more acid it will take to lower it, but not in a straight line progression. It's exponential. Even TA affects the acid dose.

The TA reduction is generally accurate when dealing with acid.

 

[Wildcat]

OK, I think I got it. Add and then test to see the real effect. PH seems to be one of the more incalculable things compared to CL, CYA, CH, and TA

 

[Wildcat]

One other thought, my trichlor, though in original package and stored at about 75 degrees is two years old. Doe the CYA and CL degrade over time like bleach?

 

[pooldv]

No, not nearly as much. Should be fine.