Three Letters Re: Clarification on Calcium Hypochlorite for Water Purification

It has been almost 20 years since I had a chemistry class, so you may want to check this with a chemist. Wanderer posted the following comment:

“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.”

He was referring to the EPA web site comment:

“… since the calcium hypochlorite has an available chlorine equal to 70 percent of its weight.”

The Wanderer’s comment about his purchase making 50% available chlorine is not quite right. Calcium hypochlorite, Ca(ClO)2 will ‘release’ chlorine and oxygen ions when mixed with water. The EPA comment actually means that pure calcium hypochlorite can release enough chlorine ions equal to 70% of the weight of the amount of the compound used. For instance, if 1 ounce of pure calcium hypochlorite is mixed with water, 0.7 ounces of chlorine ions will be released. If the mixture that Wanderer bought is 50% inert, then using one ounce will only release 0.35 ounces of chlorine ions. Also, I am not sure of the density of calcium hypochlorite, but any measurement like this should be sure to differentiate between mass and weight. If the density is close to one, then using a volume measure for ‘ounce’ is probably good enough. If not, then the amount used should probably be measured on reasonably accurate scale (and not a balance). Please check my work if you can.
Thanks, – M.W.

I have found granular calcium hypochlorite at our local Kinetico (water softener) store. They sell a package of two 8 oz bottles distributed by a company called Better Water Ind., Inc. 209 North Tyler Street, Tyler, MN 56178, phone: 507-247-5929. [At their site] click on their “products” link and scroll down to “BWI Certified Chlorine.” I notice that they have [packaging ] available from 3.5 pound jars up to 100 pound drums! The product is sold as a well sanitizer pack called “Well Safe” and comes with one 8 oz bottle of granulated chlorine (73% calcium hypochlorite) and one 8 oz bottle of chlorine pellets that are 73% calcium hypochlorinate.- Opus

Good Evening:
I also went to my pool supply store to obtain calcium hypochlorite. They had Poolife brand “TurboShock.” It was $14.85 for 5 pounds. Active ingredient:calcium hypochlorite 78% and other ingredients 22%. No one was aware of the substance of the other ingredient. I called the National Poison Control Hotline to find out. They also stated the ingredient was not known but, was a [inert] filler of sorts and not harmful.
I’m satisfied. I could decontaminate my well and everything else [for a long time] with 20 pounds of Turboshock. – Lauralei