I have used almost 2 gallons just drinking when it was 100+F and I was strenuously working. I have also drank a gallon sitting on my ass when I was eating a high protein low carb diet and it was warmish ~80F. I plan for 2 gallons per person per day if we will be performing manual labor, plus cooking dried foods and keeping clean. I have 2 fifty gallon water heater with ball valves for ease of draining and anti-backflow check valves installed to prevent water from being sucked back out of them. So I start with a little more than 2 weeks for my family of 3 right there. I would probably last 3 weeks if we are vigilant. Then it is time to tap the 110gallons in the garage. If I have warning, then I will have another 100ish gallons filled. I also know where all three springs are within walking distance and have two rigs for carrying 5 gallon jerry cans. Would also be collecting rain water.
If my math is correct then you could just add 1.1grains of sodium hypochlorite to 2 gallons of drinking water to disinfect. (Figure most of us have a reloading scale.)
1/4oz per 2 gal=1/8oz per gallon = 0.0078125lbs per gallon = 54.6875 grain per gallon. Used at 1 to 100. That would be 0.546875grains per gallon We round that to 0.55 grains which would be 1.1grains per 2 gallons, which is a real easy measurement.