Letter Re: An Alternative to Calcium Hypochlorite, by TLS


I just read the excellent article written on chlorine usage for water disinfection. As a long time analytical chemist, it was a pleasure to read such an articulate article on the subject. I wanted to add a caveat to the article. One must keep in mind that when using chlorine, a minimum contact time of one hour is required to kill organisms, and you should maintain a residual of chlorine in the water.

Contact time is the length of time the chlorine is allowed to work. And since the chlorine reacts with the organic molecules composing the undesirable organisms, its concentration drops over that time period. So the calculated the amount of chlorine to use to get to 1 ppm free (or residual) chlorine will vary based on the amount of organic material in the water. In laymen terms, the dirtier the water the longer the contact time and the higher the concentration of chlorine that is required. In normal times, chlorine is added, the chlorine is allowed to react, and the water is tested to determine free (residual) chlorine. If the residual is too low, more chlorine is added.

The maximum recommended residual chlorine level in drinking water is 4 ppm. Keep this in mind when using any chemical to treat drinking water: For the greatest safety margin, you must add enough to kill the organisms and leave a residual amount of chlorine in the water. Temperature will also greatly affect the amount of contact time required. The reaction of chlorine with undesirable organisms goes slower in cold water than warm. Keep up the good work. – JP in Kalamazoo

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One thing that hit me (while buying something to de-ice my walkways) was that I rarely see salt – sodium chloride – listed as something preppers need to stock up on, but it is something you need to consume to live, not to mention the other uses. The article on Calcium Hypochlorite (Chlorine generator) alternatives mentioned “adding salt” and that the chlorine generators turn salt into chlorination. Salt is something I get from the same store shelves as everything else, so it might be a good idea to get an extra bag of rock-salt and store it away.

I also should mention that there were several responses giving the shortcomings of running razor wire in the interior of your house. Yet I’m glad someone at least submitted the idea. It helped to have a new idea, and even if it wasn’t so good as presented it provoked a lot of discussion and several refinements and alternatives. I’d rather not discourage the inventiveness but instead look at all ideas as something to be evaluated and thought through. – T.Z.