I have been calculating the bather waste dosing as (source: http://goo.gl/thzO2i):
3-1/2 teaspoons of Dichlor
or
5 fluid ounces of 6% bleach (e.g. Clorox regular unscented)
or
7 teaspoons of MPS non-chlorine shock
per person per hour
So for my last calculation, I thought I was being very generous with the sanitizer: 2 (people) x 5 fl oz 6% bleach = 10 fl oz of 6% bleach to oxidize the bather waste. Then to bring the tub up to 4 ppm from 0 ppm chlorine, per thepoolcalculator.com, I added an additional 3 oz of 6% bleach (calculator only called for 2.8 oz). Converting 13 oz to cups, this would be 1.625 cups of 6% bleach. Do you still think I am under calculating my dosing?
As far as leaving for vacations, I think if I drop the temperature to 80 degrees, use the Nature2 stick, and shock, I should be good for a week at a time. I can have someone come over every week and re-shock it, to last for another week. I'm still a bit unclear on the whole shocking process. Can that be done with any of the sanitizers (bleach, dichlor, or MPS)? When you say to shock it, what PPM should you calculate the jump for? 10ppm or 20ppm?
I had a tough time deciding between chloring and bromine when starting my spa. I went with chlorine because that is what most people around me were using. However, with bromine being easier, I'm wondering if I should have went with that? Why is bromine not as good if you use your spa often?
As far as keeping the cover off when adding chlorine... My spa is currently connected to 110 electrical source, so the temp usually drops from 102 to 100 by the time we are done using it. That means the heater kicks on to bring it back to temp, and forces the low speed pump to run until its back to 102. Will that be sufficient for adding chlorine? I'll just set a timer for 15 minutes, then come back and close it up.