Forum Title: Closing bleach addition shot up ph
I am getting my pool closed tomorrow so I wanted to lower my ph to 7.4 (because I know it will creep up). I tested using the TFT100 kit (and checked it with my ph meter) and got 7.6 with the meter and just over 7.5 with the TFT100. I then added the requisite acid to lower it to about 7.4 But around the same time I added a lot of Clorox regular bleach to get my FC to 19 (was at about 5). The bleach bottle looked the same as last year but it said with Cloromax technology on the bottle, and I don't recall if last years bleach said that. Well after adding a little more than half the bleach I checked the ph a couple of hours later and I was shocked to see it was 8.2. I then added the rest of the bleach, and two hours after that it was 8.5 (TFT test kit showed it greater than 8.2 and my meter (which has been accurate all year) showed it as 8.5. I recall reading that the bleach should not raise the ph so I was surprised. When I close my pool tomorrow, I would like the PH around 7.4, so I wasn't sure if I should add acid tonight or not because I wasn't sure if the bleach was giving me a false ph reading. I ended up adding acid (but not enough to lower it to 7.4) and will check it tomorrow morning and then add more acid if need be. Has anyone else experienced this? I don't think this happened to me last year. If relevant, the rest of my numbers are CH 300 and TA 70. I haven't tested my CYA in a while but it was 40-50 last time I checked. I will test it tomorrow. Thanks
Category: pool Post By: LUCILLE HANSON (West Palm Beach, FL), 03/19/2019

From the Deep End - a post on chlorine and pH Technically, bleach does raise the PH right when you add it, but then as the chlorine gets used up the PH comes back down. Over time the PH change from bleach is very nearly zero. Click to expand... So, if you raised your FC quickly, it does raise pH. Your drop test for pH is effected by the high FC and the reading is not correct above FC 10. I do not know if the meter is effected. The Cloromax bleach should not be used. It has polymers in it that we do not know what effect they may have in pool water. Clorox was contacted by a member earlier this year and they stated to not use the Cloromax bleach in a pool. Take care.

- DANIELLE FULLER (Anderson, IN), 04/13/2019

Bleach, when added to water, will temporarily raise pH. Oxidation and sanitation reactions of chlorine are acidic and will lower pH by the same amount. There is a small, excess lye content to bleach that will slightly raise TA over time. Your water is probably so clean at this point and the chemical reactions are so slow that you are seeing the temporary increase in pH. How high is your FC? You can?t reliably measure pH with the phenol red indicator when the FC is over 10ppm. Your pH probe should be more immune to it but high oxidizer levels can mess up cheap pH meters as well. You could add some acid to bring it down to 7.8 and it will be fine.

- BILLIE DENNIS (Clarksville, TN), 04/15/2019

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