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How to make your drinking water safe when you can't boil it

​​If I can’t boil my water during a boil water advisory, how can I make the water safer to drink?

Boiling water for 1 minute is always the best way to disinfect (to kill germs in) your water during a boil water advisory. But if you can’t boil water (for example, the power is out during a very bad storm), you can do one of the following:

  • Use disinfectants like chlorine or iodine to kill most germs that may be in the drinking water.
  • Buy bottled water from a safe source.

Will chlorine and iodine make the water safer?

Chlorine and iodine work well to kill bacteria and viruses. However, these disinfectants will not kill parasites like Cryptosporidium. It can be hard to know if there’s a risk of parasites, especially in an emergency. If you can’t boil water, the best way to make water safe is by doing more than 1 type of treatment.

What treatment can make my water safe from parasites?

You have to treat for parasites before you disinfect with chlorine or iodine. Before you use chlorine or iodine to disinfect water, use one of these treatments to remove parasites:

  • Filter: You can buy filters at water treatment suppliers or hardware stores. Buy a filter that is rated at 1 micron absolute or smaller with a cyst rating of NSF 53 or 58 certification. After you filter the water, disinfect it with chlorine or iodine.
  • UV disinfection pen: You can buy UV disinfectant pens at camping supply stores. The water needs to be very clear (not cloudy) for the UV treatment to work. Let the water sit in a container until any particles (sediment) settle before you treat it. UV disinfection pens aren’t usually certified by a recognized agency, so you have to follow the exact instructions. After the UV treatment, disinfect the water with chlorine or iodine.

How do I disinfect drinking water with chlorine?

You can use water purification tablets or bleach to chlorinate your water.

Water purification tablets

You can buy the tablets from most outdoor supply or camping stores. Follow the directions on the package.

Bleach

To chlorinate your water using bleach, you will need:

  • a 1-litre container
  • a medicine dropper
  • unscented household bleach (5.25% sodium hypochlorite)

If your water is clear:

  1. Add 2 drops of bleach to 1 litre of water.
  2. Mix the water very well and let it stand for 30 minutes. If there is a slight chlorine smell and the water looks clear, it’s safe to drink.

If your water is cloudy:

  1. Add 4 drops of bleach to 1 litre of water.
  2. Mix the water very well and let it stand for 30 minutes. If there is no chlorine smell, add 4 more drops of bleach and let the water stand for another 30 minutes. If there is a slight chlorine smell and the water looks clear, it’s safe to drink.

How do I disinfect drinking water with iodine?

Don’t use iodine for more than 3 weeks each summer (in controlled doses) because there is a risk of thyroid problems and iodine sensitivity.

Don’t drink water disinfected with iodine if you:

  • are pregnant
  • have a thyroid problem
  • are very sensitive to iodine

To disinfect water with iodine, you need liquid iodine (2%) or iodine tablets. If you use tablets, follow the directions on the package. If you use liquid iodine, follow the directions listed below. You can buy iodine at most drugstores and some outdoor supply or camping stores.

Liquid iodine works best when you add it to warm water at a temperature of 20˚C (68˚F).

  • To treat warm water, add 5 drops (0.25 mL) of iodine to 1 litre of water. Mix the iodine and water together. Let it stand for at least 30 minutes before drinking.
  • To treat cold water at a temperature between 5 to 15˚C (41 to 59˚F), use the same amounts as for warm water, but let it stand for 40 minutes before drinking.
  • If the water is cloudy, add 10 drops (0.50 mL) of iodine to 1 litre of water and let it stand for the times listed above, depending on whether the water is warm or cold.

If you have any questions about your water, call an Alberta Health Services Environmental Public Health office in your area.



Current as of: February 18, 2021

Author: Environmental Public Health, Alberta Health Services