Chlorine Depletion Rate????

[chem geek]

I have to ask, why are you considering shocking your pool if your CC is 0? Unless your CC is significant (> 0.5) or you have algae, you probably don't need to shock your pool. Of course, you still have the issue of not attending to your pool for several days so you will need to add more chlorine to ensure it doesn't get used up. If you put in 20 ppm into your pool, then it might get used up as follows if my 0.5/1.5 assumption was correct:

Start: 20 ppm
1 Day: 14.5 ppm
2 Days: 10.4 ppm
3 Days: 7.3 ppm
4 Days: 5.0 ppm
5 Days: 3.3 ppm

So you can see how you can get down to much lower chlorine levels than your initial assumption. The easiest way to prevent this it to stop the primary source of the loss which is probably the breakdown from sunlight, but that means putting on some sort of opaque cover over your pool -- even a solar cover is better than nothing as it probably cuts down much of the transmission of UV (I'm speculating here). [EDIT] You can even cover just part of your pool, say half to 3/4ths, and keep your pool pump on its normal cycle to get the combined benefit of reduced chlorine loss while still having some of the pool water exposed to get rid of disinfection byproducts (including the main ones of nitrogen and carbon dioxide gases as well as the bad ones of volatile THMs). Of course, keeping such a pool cover "in-place" with circulating water is an engineering challenge. [END-EDIT]

Richard