pH Increase during SLAM?


Well-known member
Aug 14, 2018
Scottsdale, AZ
Hi all, I have had an algae problem for a couple months toward the end of summer, but opted to keep chlorine high and brush often since the water was still (mostly) clear and I was traveling or not available for a free weekend for a while. There was yellow accumulating on the walls after a few days without brushing or keeping FC above 10. I definitely lapsed adding enough bleach each night too, which is why the algae probably started. Anyway started SLAM Saturday:

Pre-SLAM test results:
FC: 7.0
CC: 0.5
CH: 425
TA: 120
CYA: 70
PH: 8.2--> 7.2 before starting SLAM.

Brushed everything, then left floaties and brush/pole/skimmer in pool and raised FC to 28. Kept FC between 24-30 for 55 hrs so far with pump running constantly, backwashed Sunday, brushed everyday. Pool water has gone from cloudy to sparkling clear. Doing an overnight FC drop test tonight to see if it will pass. My question is I tested the pH this evening and it had climbed back to 8.0. What would cause that? All I've been adding is bleach. Could it be a result of the FC killing algae? Thanks!


Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
pH testing is invalid when FC is above 10 ppm. It will read abnormally high.

Only test FC when following the SLAM process.