PH dropping after adding CYA

[Bvacchiano]

I added 17 oz of dry CYA to my pool as per Pool Math to bring it from 60 to 70. I tested my PH beforehand and it was 7.8. The next day I tested PH and it is a no brainer 7.5. I’ve done this several times before when adding CYA with same result.. Is this common? I realize it’s an “acid”. Point being it would be nice to include a statement like “expect your PH to drop when you add CYA” or something like “ensure your PH is not at 7.2-7.3 before adding CYA” in Pool School.

What is relationship between CYA and Ph??

 

[mknauss]

If you look at PoolMath it tells you what change in pH will occur when you add the CYA.
I used Effect of Adding Chemicals with your volume pool and it shows it will add 9.4 ppm CYA and lower pH by 0.2.

 

[Oly]

Use Pool Math.
I plugged in your gallons and at the bottom under "Effects of adding Chemicals" input 17oz of Stabilizer and it calculated this:
Raise CYA by 9.4 and lower pH by .17

 

[Texas Splash]

Like the others, I used the new Poolmath tool and it does say in the "Effects of Adding Chemicals" that 17 ounces will lower the pH by 0.2. So to answer your question, yes, changes (to some degree) are common when adding chemicals. All of us as users have to check the "Effects of Adding Chemicals" to see what impact adding chemicals will do. Overtime, we learn to expect those side effects, but once it a while we get surprised. If it helps at all, the pH change is relatively small in the overall scheme of things, and I suspect it will climb back up soon.

 

[Divin Dave]

A drop in pH is expected, and not necessarily a bad thing. I look on the positive side, as killing 2 birds with one stone.