CL loss

CBpoolguy

In The Industry
May 1, 2024
2
Charleston
100,000 gallon plastered pool. Losing CL but not losing cya. Can start the day at a 12 in CL but 8hrs later it has dropped to a 1. Its not getting fresh water so thats not the issue and like I said cya level is staying at an 80. Any ideas why I would be losing CL that quickly
 
Can we see a picture of this pool? That is commercial sized. How are you testing your water? How do you chlorinate? What is the swimmer load?
 
New build it is commercial. No swimmer load yet and we are using trichlor feeder

Generally with high Chlorine usage, a SLAM is recommended. For your CYA level that is a FC level of 31.

 
Also - why is your CYA so high on a new build? Did you mean to add that much? That pool is almost to the point of being unmanageable. Are you using stabilized trichlor?
 
For every 10 CYA, the FC needs to increase proportionately to match. This may be against local codes for commercial pools so they often have a UV/Ozone system to aid in sanitizing.

All lines on this chart are equal for sanitizing:

lc_chart.jpg

This early in the season, 2 or 3 FC lost daily is reasonable in such a large pool (with no bather load yet). Losing considerably more than that points to algae, likely from the CYA being higher without an appropriate FC.