Funny CYA and FC reading.

Tyrone Shuz · Jun 2, 2020

I decided on liquid stabilizer and poured in two gallons (roughly 20k gallon vinyl IG pool). I'm supposed to get 32ppm out of that, but it's reading less than that, between 20 and 25. I also put in three bags of 65% avail cal hypo (can't find bleach) and a day later I'm getting a FC reading of 1, and a CC of 1. The daily color test agrees with this (I know they're unreliable after lots of chlorine is put in the pool). Does liquid stabilizer give a different reading? Are my reagents bad? The DPD powder is clumping. I ordered a new refill kit from TFT but it'll be a few days before I get it. I also ordered another gallon of stabilizer.

20,000 gal IG Vinyl, sta-rite 3/4 HP Pump, DE filter (Hayward I think) w/multiport

mknauss · Jun 2, 2020

A CYA reading above 20 is viewed as 30. So that is close to your expected level of 32 (which you cannot test to that accuracy).

Sunlight or organics consume chlorine. So one, or both, consumed the chlorine.

Tyrone Shuz · Jun 2, 2020

Thanks for the reply! Hasn't been all that sunny, the three bags should have added 12ppm of FC. To be down to 1 in one day is alarming. A couple small algae spots and still some schmutz on the bottom that the robot is gradually picking up. Another gallon should bring me to 40-45, and I think I've found a source for 12% liquid chlorine. My CH reading is only 100 so I can use the remaining 18 bags of Cal Hypo w/o worrying about scaling.

mknauss · Jun 2, 2020

If you have visible algae, with that chlorine loss, you need to follow the SLAM Process

Tyrone Shuz · Jun 3, 2020

I did--Raised it 12ppm was very surprised that it was gone so quickly.

Flying Tivo · Jun 3, 2020

You caught it just in time. Keep the slam levels until you pass the Overnight Chlorine Loss Test.

splashpad · Jun 3, 2020

Tyrone Shuz said:
I did--Raised it 12ppm was very surprised that it was gone so quickly.

I would add another dose and test about 15-30min later.
Then after a hour or so, test again (if that first test showed the expected level of FC), esp if you suspect that your FC is being "used up". Which a CC of 1 would definitely suggest.

Can you get some plain household bleach? (not sure of your location) Something to get chlorine in the pool

Tyrone Shuz · Jun 14, 2020

Bleach has become impossible to get, though I can get the 12% at a semi-nearby pool store. I'm thinking about converting to SWG, because I'd so much rather use bleach than cal hypo.