Is there a formula you can use to find out how long it takes for your water to fully cycle through? I had to backwash this morning and add more water. I tested the cl right after and it was at about 12 (where I need it to kill the algae). About 4 hours later I tested again and it was only 2. I guess what I need to know is when would have the most optimal time for me to have rechecked the cl in order to make sure my level stayed at 12? Thanks guys!