Hello James,
In reading your post on Tuesday May 16th on Water Purification, I have done some looking into this important topic. The link you provided from the EPA web site states below verbatim:
“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 above.”
I stopped at the local pool supply store to inquire about what they would recommend for drinking water purification. I was brought to everything but Calcium Hypochlorite. I had to ask the employee if he could verify this because it is important that I not get the wrong item. He continued to say “…this is what you want…” I asked another employee that was not privy to my discussion, and she said,…. “…this here is what you want…” Again, not the product I was looking for. In fact out of four employees, I was shown four different products. The female clerk was very inquisitive and very insistent. I told her that I thought it had calcium in it and she became even more awkward. I felt as if I was to be added to some list just for wanting to purify my water. I left there with the wrong product and was asked for my name on the receipt, (I paid cash). I wanted to bring this up as my guess is that there are those who choose to do something “illegal” with this product and it makes it harder for normal law abiding folk like myself to purchase.
I stopped at the local Big Box lumber yard and they had Calcium Hypochlorite, (a.k.a. Pool Shock) it was concerning as it states 50% Calcium Hypochlorite and 50% Other Ingredients. Making it a 50% available Chlorine.
In common language, … is this adequate? It does not seem to be of the 70% goal you mentioned on your earlier post. I think there is an equation that we need that is missing. The EPA site states there is an available 70% chlorine based on weight. Is this to be constructed as true for ALL Calcium Hypochlorite being equal to this ratio? What about the 50% OTHER INGREDIENTS? To make things more confusing, they offered another brand of this that had 47% Calcium Hypochlorite.
Please help close the gap on this topic as it is such an important one. – The Wanderer
JWR Replies: The problem with most retail store employees these is that they are marginally qualified to run a cash register, but little else. To most of them pool water chemistry is an arcane art–not rational science. Don’t ask them chemistry questions!
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.ou want to buy 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.
Re: > What about the 50% OTHER INGREDIENTS?
Those are most likely inert filler. But that may differ widely, depending on maker/brand. You’ll have to look at the label carefully. Be certain that there are no other chemicals, dyes, scents, et cetera before using any chlorine product for water purification!