Consistently Losing Chlorine

[stingr07]

Asking for a friend.

20k gallon IG vinyl-lined pool with sand filter. Little Rock, AR area.

Since July (when temps climbed to 95+), he has been having a real problem keeping chlorine in the pool. He had an algae bloom but got rid of that with water back to clear. Added 2lbs of shock (Leslie's Power Powder Plus) at noon on 8/3. Checked levels at 10pm and FC was 2ppm, ph was 7.8, TA was 90, CH was 90, and CYA was 30. Took levels again 19 hours later, FC was 0 and other levels were the same. Question is why does his chlorine drop from 2ppm to 0ppm in 19 hours? Air temp was 100 degrees that day with water temp of 89 degrees. Is the high temps to blame for this?

Appreciate any info!

 

[tim5055]

Welcome to TFP!!

My guess is that not all algae has been eliminated from the pool. The only way to be sure is to conduct an Overnight FC Loss Test (OCLT) using a test kit that has a FAS-DPD chlorine test that can discriminate down to .2ppm chlorine.

How much Pool School have you read? Start with these:
ABCs of Water Chemistry
Recommended Pool Chemicals
How to Chlorinate Your Pool

 

[stingr07]

Appreciate the suggestion!

Will give this a try and will post the results!

 

[pooldv]

It is normal for a pool to consume 2-4ppm per day. With FC at 0 it is a good idea to do the Overnight Chlorine Loss Test to see if some algae is growing. It is important to keep FC above minimum for your CYA at all times to keep the pool sanitiz3d and algae free. [FC/CYA][/FC/CYA]