Is this possible?

[dojiboy]

Just got done shocking my pool for about 3 days. I hadn't tested PH during this time because I read on this site that PH test is unreliable at high chlorine levels. With CYA=60, I was shocking in the FC=high 20s.

FC is now down to 10.5ppm and I tested PH expecting it to be high since I shocked with liquid chlorine.

However, PH has gone from 7.6 down to 7.0-7.2 during shocking.

Is this possible? I've run the test several times to be sure.

To summarize

FC=10.5
CC=.5
TC=11.0
CYA=60
TA=70
PH=7.2
CH=250

According to pool calculator, about 3lbs of Borax should do it, but I was expecting to have to add acid.

I did use a little chlorine neutralizer to get FC down before a play date. Not sure if that could drop the PH.

Thanks

Doji

 

[JamesW]

What did you use to shock?

 

[dojiboy]

since I shocked with liquid chlorine.

 

[JasonLion]

Possible: certainly, even though it is not what I would expect.

There are a couple of different kinds of chlorine neutralizers. Most of them are more or less PH neutral, but some lower the PH.