Where is the Chlorine Going

[John Kearns]

New to taking care of pool chemistry on my own after 11 years of relying on the Pool Store. My SW pool's water had a greenish tint for the first time ever this spring. I bought the TF-100 test kit and got the following numbers:

FC: 0.5
CC: 3
PH: 7.5
CH: 225
TA: 110
CYA: 50

Decided to shock and added 10 lbs of 65% Cal_Hypo (more than the pool calculator recommended, and I know the danger of raising the CH, but it's what I had on hand).

In any event, the pool looks absolutely great now, crystal clear, but the new numbers aren't much better:

FC: 0.5
CC: 0.5
CH: 275
TA: 70
CYA: 70
Borates: 40 (I didn't have this test first time around).

As I said the pool looks great. I'm in RI, so it hasn't been very warm. So where did all the chlorine go? And do I SLAM again. I have purchased 12.5% bleach if need be.

Thanks from the Newbie.

 

[Swampwoman]

Welcome to TFP.
It is possible nascent algae is using your chlorine...or also possible that you need to dial in your SWG. Technically, it sounds as if you didn't really slam (as in maintain) if you just "shocked" but the best way to tell if you need to slam is to do the overnight chlorine loss test detailed in the Slam instructions -- with te swg off.

How long and at what percentage are you running your SWG?
I'd hazard a guess that may need to be bumped up.

However, why not add the amount of liquid chlorine you need for you chlorine:cya ratio (see chart/link in my signature) and see if it holds via te OCL test and if so, then see if your swg can produce enough to keep it there...and if not, slam!

 

[John Kearns]

Thanks.

After re-reading the SLAM section, I realize I shocked, but didn't maintain. Back to work.

 

[Divin Dave]

Yup. Slamming is a process, not a 1 time treatment.

When you have CC of .5 or less (1 drop to clear) and you pass the OCLT, and the pool is crystal clear, then you can consider the slam successful and drop the FC back down to regular maintenance levels.

Thanks.

After re-reading the SLAM section, I realize I shocked, but didn't maintain. Back to work.