Possible PH goof during a SLAM


Active member
Oct 21, 2018
Northern Tennessee
I started a SLAM on Thursday. It rained non-stop for 12 hours during the SLAM on Friday and I didn't go out and test or add any chlorine during that time. I went out an hour after it stopped raining and tested the PH since I was worried that the rain increased it. It said that it was 8.0 so I lowered it (it was 7.4 before starting the SLAM). I stupidly forgot to test the chlorine level to make sure it was lower than 10 when I did this, however. When I went to test the chlorine an hour after adding the muriatic acid, I discovered that the chlorine level was actually 12 ppm so the PH test probably wasn't accurate. I still can't believe that it only went down 4 ppms in 14 hours but that is what the test indicated. I went ahead and resumed the SLAM since I didn't want to miss out on the benefits of a night-time shocking. If PH was actually still 7.4 where it was before it started raining, I probably added enough acid to lower it to 7.0 (or possibly a bit lower) according to the pool math calculator. TA is only 50. Do I need to let the chlorine drift down below 10 today so I can retest it, and then bump it up if needed? Water went from a dark green to a pale green overnight, and I can now clearly see the bottom so I hate to delay the SLAM to test the PH unless it is needed. Since the chlorine raises the PH, do I even have to worry about PH of 7.0 or even 6.8 causing any problems? I tested the water at a 14 ppm chlorine level a little while ago and it says PH appears to be around 8.0 again, but I know this isn't accurate due to the high chlorine level.


Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
Test your TA. If still 50 or so, no issues.

Chlorine does not raise pH. When you add sodium hypochlorite to your pool water, the chemical reaction is pH neutral in your pool.