chlorine level ?

[chem geek]

That is interesting. So let me get this straight. Did you keep the solar cover on when you added the chlorine (presumably just moving it aside when you poured in the chlorine)? If so, then that would imply a loss from UV getting through the clear cover. I thought that the covers wouldn't let much UV through (visible light, yes, but not UV). If possible, it would be worth seeing if the same problem happens when the sun isn't on the pool.

I don't know anything about why the FAS-DPD test would go from red to pewter. The Taylor instructions say that high chlorine above 25 ppm (near where you are measuring) can result in a brown color and that to handle that you should either use more powder (they don't say how much, but I'd guess double the amount, or 4 scoops total -- at least for the Taylor kit since I'm not sure what Ben's uses) OR you can dilute the sample using filtered or bottled water and then multiply the result by your dilution ratio.

Richard