Chlorine Loss

[ac130loadmaster]

I finally have my pool balanced and clear. The only piece of the puzzle I am missing is the correct CYA number. A few days ago I put in approximately 4 lbs of stabilizer. I put it in the skimmer, but ended up backwashing for a few minutes the next day. My CYA registered 0 when I tested it for the first time after opening the pool. I closed the pool with about 50 ppm CYA in the winter. So I assume there is residual CYA left over and I am truly not at zero. I finally did the overnight FC drop test and started out at 18.5 FC after sundown. The next morning before any sun hit the water I still had 18.5 FC and zero CC's. Yaay. So outta curiosity, I didn't add anymore chlorine all day. After the sun went down my FC dropped to 2.5 with the sun being on it for about 13 hours. So I am assuming that since I passed the overnite FC drop test, the only thing that burned the chlorine was the sun. Since I really don't know my CYA level and been assuming 30 for the moment, is the 16.0 ppm FC drop normal or do I need to assume I still have low CYA level of maybe 10 or 15 and add a couple pounds more stabilizer?

Also my father in law mentioned chlorine granules and using them to make my own chlorine. Said it is something he used to do when he was younger and I could possibly save money making my own. Since I have never heard of it mentioned here I am thinking that this isn't the way to go. But I had to kill his curiosity.

Thanks again for all the help.

Al

 

[chem geek]

Let's figure that the 13 hours is equivalent to around 8 hours of direct noontime sun (it might be somewhat more, but let's just use this). Your chlorine dropped by x⁸ = 2.5/18.5 so x = 0.78 so 22% per hour. If you had absolutely zero CYA in the water, then it would drop around 50% per hour, so it sounds like you've got around 10 ppm CYA in the pool right now. So yes, why don't you figure on around 15 ppm so as not to overshoot.

 

[JasonLion]

You can make "bleach" out of dichlor or cal-hypo by mxing with water. You aren't making chlorine, just converting solid chlorine, which is easy to carry, into liquid chlorine which is convenient to use around the house.

 

[ac130loadmaster]

Let's figure that the 13 hours is equivalent to around 8 hours of direct noontime sun (it might be somewhat more, but let's just use this). Your chlorine dropped by x⁸ = 2.5/18.5 so x = 0.78 so 22% per hour. If you had absolutely zero CYA in the water, then it would drop around 50% per hour, so it sounds like you've got around 10 ppm CYA in the pool right now. So yes, why don't you figure on around 15 ppm so as not to overshoot.

Thank you very much. I will shoot for an additional 15ppm. And test again in about a week.

 

[ac130loadmaster]

You can make "bleach" out of dichlor or cal-hypo by mxing with water. You aren't making chlorine, just converting solid chlorine, which is easy to carry, into liquid chlorine which is convenient to use around the house.

Ill just stick with the 6% liquid bleach. Thanks much