Two nights ago at about 11:00pm there were about 9 slightly drunk teens enjoying the pool for about an hour. I expected the chlorine to be low the following mourning but it was only down 1ppm from what I was expecting. The following day with the cover on and no usage and 2ppm chlorine added the level was about 1ppm lower then normal. The question is how quickly does chlorine get used up after a pool party, is the demand still high for many hours after the high bather load?