You go in your 44,000 gallon pool of cool water for a few hours and you might sweat out a couple ounces of sweat and it is diluted in 44,000 gallons of water. You go in your 400 gallon hot tub at 103 degrees and in a hour you might sweat out a quart of water per person and it is diluted in 400 gallons of water. Along with sweat you dissolve body lotions and skin oils. You get laundry products from swimsuits etc. you do this every day for 3 months. What I have found happens in a hot tub is it takes off really fast once the sanitizer hits zero and it has a little time on the water. When I was trying to keep my level very low all the time with a feeder. With dosing the tub after using it in the evening, I found if I bring it up to 5ppm let it breath for a few minutes running the clean cycle and then closing it up the next day it is 1ppm and crystal clear and ready for use. Let the sanitizer work over night kill the stuff filter it out and then get in low chlorine water.
When I see how small amount of Clorox I add to 500 gallons of water to get 5ppm and then I think about how much Clorox people will put in a bucket of water when cleaning and not worry about it.
Once your water goes south and you try and correct it and find no amount of shocking will correct it and you end up draining and flushing. You will see staying ahead of the curve is exactly what you need to do you are right.
For me the margin of error trying to stay at .5 ppm is just too thin and you will get a day where you have 6 people in the tub rather than the normal 2 and maybe high pollen count in the air or a million other things and there isn’t enough wiggle room when you are trying to run it so perfect.
I’m sure for a dealer in an indoor showroom with hardly anyone in the tub it is not hard to hit and maintain .5 – 1.0 ppm. I just never was able to work it so close. I don’t have any issue with getting in a 5ppm tub I actually feel safer than someone’s tub that is at zero worries me more.