Losing too much free chlorine

[melbogia]

Hello all, I am new to pool and recently moved to Sacramento California, where it's pretty hot lately. I have about a 15,000 gallon in-ground pool with CYA of about 25. Last night the chlorine was about 1 ppm and I added a gallon of 10% chlorine (dated 22041 so about 4 month old) and ran the pump all night to circulate it. I tested again early this morning before the sun came out and the chlorine was 7 ppm.

No swimming today and I tested chlorine just now as the sun is going down and the chlorine level is 2.5 ppm - so I lost 4.5 ppm to the sun. Is this expected loss due to sun? Admittedly it was pretty hot today - 104 degrees, and there is no shade. Chlorine was measured with the FAS-DPD test kit.

Would it help to increase CYA? How much? Otherwise it seems like I'd be adding about a gallon of liquid chlorine every night.

 

[mknauss]

In your climate a CYA of 50 ppm would be a good idea. Should keep your average FC loss each day at or below 4 ppm.

 

[melbogia]

Thanks, I'll try that

 

[jeffchap]

Did you test your FC last night after adding chlorine? It would be helpful to know how much it dropped overnight. If more than 1 ppm, you likely have some algae and need to perform a quick SLAM.

1 ppm FC is too low, even with CYA at only 25. Once you bring CYA up to 50, try to keep FC at 5 or above and never let it drop below 4.