Here is the information that I have found about using "pool shock" for water purification.
It turns out many municipalities use Granular Calcium Hypochlorite (pool shock) for treatment of their water.
Get the plain variety, with no algaecides or fungicides.
Dry chlorine, also called calcium hypochlorite has the added benefit of extended shelf life. Providing it is kept dry, cool and in an airtight
container, it may be stored up to 10 years with minimal degradation. If you want to keep chlorine in larger quantities, this is the item to store
(according to Bingo1). It must be ONLY 65% calcium hypochlorite, no additional anti-fungals or clarifiers. In an EXTREMELY well ventilated area,
(Hint: OUTSIDE!) add and dissolve one heaping teaspoon of high-test granular calcium hypochlorite (approximately 1/4 ounce) for each two gallons of
water. Five pounds of dry pool bleach costs about $10-15, which will make about 92 gallons of bleach, which will sterilize 706,560 gallons of clear
water, or 353,280 gallons of cloudy water."
From
www.epa.gov... -
"Granular Calcium Hypochlorite. Add and dissolve one heaping teaspoon of high-test granular calcium hypochlorite (approximately 1/4 ounce) for each
two gallons of water. The mixture will produce a stock chlorine solution of approximately 500 mg/L, since the calcium hypochlorite has an available
chlorine equal to 70 percent of its weight. To disinfect water, add the chlorine solution in the ratio of one part of chlorine solution to each 100
parts of water to be treated. This is roughly equal to adding 1 pint (16 oz.) of stock chlorine to each 12.5 gallons of water to be disinfected. To
remove any objectionable chlorine odor, aerate the water as described below.
The treated water should be mixed thoroughly and allowed to stand, preferably covered, for 30 minutes. The water should have a slight
chlorine odor; if not, repeat the dosage and allow the water to stand for an additional 15 minutes. If the treated water has too strong a chlorine
taste, it can be made more pleasing by allowing the water to stand exposed to the air for a few hours or by pouring it from one clean container to
another several times"
"Okay, a lot of people don't have a 12.5 gallon container laying around, so let's break it down. To make two gallons of the bleach, one heaping
teaspoon of the calcium hypochlorite goes into 2 gallons of water. To make drinkable water, 2.5 tablespoons of the bleach goes into 1 gallon of water.
Let stand covered 30 minutes, aerate to taste"
For 10-15 bucks purifying 700 thousand gallons seems like a good deal to me. I'm also assuming that some of the puri tabs are made out of this same
chemical (its just granular bleach).
I figure a bucket of this can stay up at my land for years and still be a valid purification method. I think the shelf life said 10 years!