A lot of this information has been posted on this blog in the past, however I still get questions on it so I thought I would cover purifying water with chlorine again.
I see FEMA, the American Red Cross and others all recommending liquid Clorox, Purex or chlorine as a method for purifying water in an emergency. Bleach can be a good method of water purification, except they don’t mention that liquid bleach has a shelve-life.
Clorox states on their website that bleach should be replaced every year. This is for laundry use. For purifying water, bleach has started to lose its strength at six months. It takes about 4-8 weeks from the time chlorine bleach is made to reach your home. This leaves you 3-5 months where the bleach is at the effectiveness level stated on its label.
Avoid using any bleaches that contain perfumes, dyes and other additives. Use only regular household liquid bleach that contains 5.25 to 6.0 percent sodium hypochlorite. Chlorox has recently come out with a new product “Clorox Ultra”. They have changed the concentration of Sodium Hypochlorite (chlorine) from 5.25% concentration to 6%, and they have added Sodium Hydroxide. They are doing this to reduce the size of the containers. Chlorox has stated that this is safe to use for water purification.
Clorox Ultra, Chlorox, Purex or chlorine bleach may be used to disinfect water in the following amounts. Four drops per quart gives 10 ppm in clear water. This amount should be increased to eight drops in turbid (cloudy) water. Sixteen drops will provide 10 ppm per gallon of clear water. You should be able to get a slight odor of chlorine after the water sits for the 15 minutes. If not, add more Clorox.
Warning – Chlorine will not reliably kill Giardia and Cryptosporidium. SODIS, boiling, chlorine dioxide tablets and good water filters are more reliable. While chlorine will not kill Giardia and Cryptosporidium reliably, it is effective against most other bacteria’s.
Don’t pour purified water into contaminated containers. Sanitize your water jugs first and don’t forget the threads and caps.
Chlorine Bleach Sanitizing Solution.
To sanitize containers, mix 1-tablespoon chlorine bleach into one gallon of water. Always wash and rinse items first, and then let each item soak in the chlorine bleach sanitizing solution for 2 minutes then drain and air dry.
Now maybe a good time to check the dates on any bleach you have stored and rotate it if needed.
Now let’s talk about powdered chlorine which is calcium hypochlorite. This can be used for purifying water and has no shelf life, which makes it sound perfect. However, you do have to be careful how you store and use it. Used incorrectly it can react violently and start fires.
See the following post for more information. Calcium Hypochlorite for Treating Drinking Water, The Good and the Bad.