Letter Re: Seeking Advice on Swimming Pool Chlorine for Treating Drinking Water

Mr. Rawles,
I want to buy some pool chlorine crystals for long term storage. Holly Deyo’s book had a formula for purifying large amounts of water with this product, but how would I make a chlorine bleach substitute that could be used to purify smaller quantities of water or as laundry bleach? Is there an amount in grains or grams that could be used to make up, say, five gallons at a time? I know store bought laundry bleach like Clorox has a limited shelf life, so I wanted to be able to make [my own hypochlorite solution.] Thank you for any information you could provide. – CG in North Carolina

JWR Replies: Calcium hypochlorite is available from any swimming pool supply company. A granular (dry powder) “pool shock” product that lists only Calcium Hypochlorite as the active ingredient should be safe to use for water purification. The problem with other varieties is that they include other algaecide or fungicide chemicals that are probably not safe for human consumption. Ditto for using liquid bleach for the same purpose. With those, you want to buy plain Calcium Hypochlorite bleach. Do not buy bleach with fabric softeners, scents, et cetera. Keep in mind that bleach solutions break down and weaken with time (anticipate a 24 month shelf life), but that dry granular bleach stores indefinitely. Here is a quote from an EPA web site: “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 [to create a chlorine disinfecting solution]. 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 [solution] to each 12.5 gallons of water to be disinfected. To remove any objectionable chlorine odor, aerate the water…”

SurvivalBlog reader Laurelei recently reported that she found the Poolife brand “TurboShock” available $14.85 for five pounds. For purifying drinking water, two of the five pound boxes would constitute a “lifetime supply” for most folks.