A while back, chemgeek provided some information regarding the rate at which chlorine is lost due to sunlight exposure at different concentrations of CYA. I took that information, and I came up with a series of charts that roughly predict how much FC levels will drop after each additional day passes.

This season, I have been plagued with problem pools that need to be "shocked" every week. I understand why this is happening, but unfortunately, my options are somewhat limited, and I can't necessarily do what needs to be done to correct the situation.

So because of these situations, I would like to create a chart that can roughly predict the same type of chlorine loss, but in terms of hours or even minutes. The problem is that I don't know the math involved.

My goal is to be able to approximate how long it will take before a pool will be swimable after adding a hefty dose of chlorine. That way I can try to dose a given pool such that it will be swimable by Saturday when the customer will want to swim.

Can anyone help me figure this out?