Rate of chlorine loss in a covered pool verses an uncovered pool

[steve53]

I know there is a difference, but can anyone quantify it for me? It seems like when I cover the pool the chlorine lasts a lot longer.

Thanks in advance

 

[Texas Splash]

Here was a previous discussion on that topic: What effect does having a cover have?

 

[chem geek]

The answer is temperature dependent because while the loss from sunlight depends only on the amount of sunlight (at a given FC and CYA level), the losses other than from sunlight are a function of temperature. For example, in my warm pool at 88ºF with a mostly opaque pool cover, if it's on all the time the loss is around 0.7 ppm FC. Without a cover the loss would be roughly 2 ppm FC. However, if I had a lower water temperature the loss might be less than 0.7 ppm FC so an even bigger difference.

Ironically, the chlorine losses other than from sunlight are mostly chlorine oxidizing the cover, assuming you have a clean pool and filter. There is also some lost from outgassing when the cover is off, but not that much.