Water disinfection is a critical part of our emergency plan. Properly stored water will always be your safest option when it comes to emergency drinking water. It takes up a lot of space making it difficult to store enough for an extended period of time. Water collected from a questionable source should always be treated before drinking, or using in cooking or for hygiene purposes.
Chlorine can effectively disinfect water. It is important to note that it may not deactivate some protozoa such as giardia and cryptosporidium. The American Red Cross recommends using liquid chlorine bleach with a sodium hypochlorite concentration of 5.25% to 6% as the only active ingredient. Use only plain liquid bleach with no thickeners, scents or additives. The problem with household bleach is that it has a shelf life of only 6 months. After that time the chlorine level decreases and it is less effective. Rotation is critical for it to be effective.
Powdered or granulated calcium hypochlorite is an effective option for chlorine disinfection. It has a useable shelf life of around 10 years. Calcium hypochlorite is sold as “pool shock.” It is commonly found in a powder or granulated form containing 68% calcium hypochlorite and other salts.
The positive side of the story is that a one pound bag can treat over 10,000 gallons of water. A chlorine stock solution can be made by adding 1 teaspoon of calcium hypochlorite to 1 ½ cups of water. This stock solution can be used to disinfect water just like household liquid bleach. Storing it in powdered form enables you to make small batches of fresh liquid bleach as needed. It only takes 1/8 teaspoon of powder to treat a 55 gallon barrel of water.
On the other hand, calcium hypochlorite is a dangerous chemical and requires special handling. We have some friends who stored calcium hypochlorite inside of a Metamucil bottle in the original bag with a stainless steel gravity water filter in its original box and a new glass bottle of Polar Pure. These items were placed together in a Rubbermaid tote as an emergency water kit. Two years later they opened the kit and discovered that the stainless steel had split and was completely corroded. These photos show the damage to the filter. We do not know exactly what caused the damage, but the calcium hypochlorite is definitely suspect. Be very careful how you store it and what you store it near.
It is best to store it in its original container in a cool dry place away from almost everything. According to a friend of ours who is a chemical engineer, dry calcium hypochlorite does not react with polyethylene, polypropylene, polystyrene, ryton, PVDF and Teflon. If you must change containers, make sure that both the container and lid are made materials it does not react with.
The MSDS sheet on calcium hypochlorite states that it is stable but reacts with reducing agents, combustible materials, organic materials, acids and moisture. It is extremely corrosive in the presence of aluminum, corrosive in presence of steel and slightly corrosive in the presence of glass and stainless steel. It is very hazardous if it comes in contact with skin or eyes or if it is ingested or inhaled. It is best to wear gloves, goggles and a mask when handling.
Calcium hypochlorite might be a great addition to your storage. A very small amount can treat a lot of water effectively. It can be purchased where pool supplies are sold or on Amazon.com.