First time post here. I'm following all the steps for shocking with bleach. Have a 16,000 gallon inground Pebble Tech pool and have used liquid bleach solely (with an occasional trichlor tab or two and polyquat) for about 5+ yrs now. Usually keep a close eye on the readings throughout the year, so I really have never had a problem. Haven't had the need to drain or even shock since we did the Pebble Tech about 4 yrs. ago.
Last week, I noticed a bit of green algae in a few spots around the pool.
My readings at that time were;
FC =2.0 (normally 3-4)
Alk = 120
CYA = 35-40
temp = 68*
So I began the shock treatment the night before last.
Brushed all areas. Brought the FC level up to 14. Next morning was down to FC=5.0ppm, added more bleach, brushed etc. yesterday throughout the day and eve.
This morning reading was 9.0 w/CC=0, so I added another 3 (96.oz 6%) jugs, which (after waiting about an hour to test) only brought the level up to 12ppm. So I added another two 96.oz jugs. After waiting another 1/2 hour or so, I checked again. New reading was back down to 11ppm. (CC=0).
I'm somewhat confused at this point. The green algae is gone at least. I've used a total of 18- 96oz.6% jugs so far.
I'm using the PS233 test kit (from pool solutions) (DPD powder etc.).
The only thing that *I* can think of that possibly could be a prob is my DPD powder is from last summer, and it looks just a little off-white/gray, rather than the bright white it used to be and I suppose could be giving me inaccurate FC readings???
Just wondering if anyone has any ideas, or has experienced this in the past.
Thanks in advance!