How to Sterilize Water in Case of an Emergency

Why Does Water Need to Be Sterilized? 

All water has some level of contamination. The water that gets piped into your home isn’t created in a lab somewhere but sourced from groundwater, rivers, and lakes. The water is potentially exposed to all sorts of disease-causing contaminants before it reaches you, including: 

• Microorganisms like algae or mold 
• Viruses, pathogens, and protozoa 
• Minerals and heavy metals 
• Radioactive materials 
• Synthetic chemicals and other pollution 
• Decaying matter 
• Human and animal waste  

These make water treatment absolutely necessary for the health and safety of you and your  loved ones. Municipal water suppliers and bottled water producers use various methods to sterilize your water but if for some reason you don’t have access to treated water, you need to do it yourself.  

Even the treatment methods used by municipal water suppliers don’t remove all contaminants, which is why many people install water filtration systems in their homes.  

If My Water Is Clear Should I Still Sterilize It? 

Yes. Many contaminants are too small for humans to see but they can still make you very ill. If you’ve ever looked at unfiltered water under a microscope, you know there’s a whole world of activity you otherwise would have missed.  

If you’re in a situation where the water you have access to has not been treated, even if it looks and smells OK, you should still sterilize it before drinking it. Sterilizing potentially dangerous water could save your life. 

Which Sterilization Methods Are Best? 

Each method of sterilizing water has its own advantages and disadvantages. The best methods that remove the most contaminants are distillation and reverse osmosis. These are what pharmaceutical companies use when they need purified water for drug manufacturing.  

Distillation 

Distillation is the process of turning water into steam, which leaves behind most impurities, and then recapturing the purified steam in a clean container. Distillation is a great way to sterilize water because it removes the contaminants from the water, but it requires equipment that most people just don’t have in their homes.  

Reverse Osmosis 

Reverse osmosis pushes water through a membrane with pores so small that almost nothing besides water molecules can fit through. Many contaminants, like fluoride, can only be removed using reverse osmosis or distillation.  

For a reverse osmosis system to be effective, you should have pre-filters set up that remove larger particles. The pores are so small that if you put unfiltered water through, the membrane can easily become clogged or damaged.  

Many high quality home filtration systems feature reverse osmosis like the HomeWater Under Sink 4-Stage Reverse Osmosis Water FIlter.  

What Are Methods to Sterilize Water From Home? 

While home water filtration systems can remove contaminants and improve the taste of your water, you shouldn’t rely on them in an emergency situation. The filter in a home filtration system may not be designed to handle certain contaminants. If you do use your at-home filtration systems, you should change the filters and flush the system once the emergency is over.  

To avoid the hassle and any potential damage to your filtration system, it's better to use one of the following methods recommended by the EPA and CDC.   

Filtering Through a Cloth or a Screen 

If you need to know how to sterilize water without a high-tech setup, you can use a clean cloth, a screen, or a coffee filter to remove cloudiness and bigger particles. Run dirty water through repeatedly until you are left with nothing but clear water.  

The great thing about this method is that whether you’re at home or in the woods somewhere, you probably have some sort of cloth on you. The downside is that it's not very effective against microscopic contaminants like bacteria. While it’s better than nothing, this works best as a prefilter for other methods.  

Boiling Water 

Boiling is one of the best known and oldest forms of sterilization when you don’t have access to clean water.  

In order to properly sterilize your water through boiling, first make sure it's running clear. If you have cloudy water, filter it through a cloth until it is clear. Then bring the water to a rolling boil for 1 minute (3 minutes for high altitudes) before taking it off the heat. Boiling water can leave it a little flat tasting, but a small pinch of salt per quart of water can help bring some life back to it.  

The great thing about boiling water is that it's easy and you can do it at home or while outdoors. The negative is that it doesn’t actually remove anything from the water like other filtration methods. Still, this should be your first go-to if you need drinkable water. If you can’t boil water for some reason, using bleach or iodine is your next best option.  

Chemical Disinfection 

If you don’t have a way to boil water, household bleach can help. Make sure you use regular, unscented, liquid chlorine bleach. Do not use color-safe bleach or anything with added cleaners or chemicals.  

The label should say the active ingredient is 6% or 8.25% of sodium hypochlorite. This is important because it will tell you the amount of bleach to use.  

Make sure you are in a well-ventilated area and that the water you’re disinfecting is clear. If it's cloudy, filter it with a cloth or coffee filter until it’s clear. 

For a 8.25% concentration, add six drops of bleach per gallon of water into a clean container.  

For a 6% concentration, add eight drops per gallon of water into a clean container.  

Once added, stir the water and bleach mixture and let it sit uncovered for 30 minutes. If the bleach smell is too strong after 30 minutes, you can pour it back and forth between clean containers a few times until the scent gets weaker.  

Iodine 

If you don’t have bleach, check your medicine cabinet or first aid kit for iodine. If your water is clear, add five drops of a 2% iodine solution to 1 quart of water. If it's cloudy, add 10 drops. Stir the iodine into the water and let the mixture sit for 30 minutes.  

Water Disinfection Tablets 

When it comes to how to sterilize water, these tablets offer a simple solution. You can find water disinfection tablets in stores that sell outdoor equipment. These tablets might be a great solution if you’re going camping and you won’t be able to boil water. They come in many different types, so make sure you check the label for proper usage instructions.  

Can I Use a Water Pitcher Filter (Activated Charcoal) to Sterilize Water?  

Most pitcher filters use some form of activated carbon because it improves the odor and taste of tap water. Activated carbon works by attracting certain contaminants and absorbing them so the water on the other side comes out cleaner.  

While these water pitcher filters with activated carbon improve your water quality in various ways, they’re not recommended as water sterilizers by themselves because they don’t work against pathogens.  

Once you boil or otherwise disinfect your water using the methods above, these pitchers can be used for an added layer of protection. If you use bleach to disinfect your water, these can also be good to remove that slight chlorine odor and taste. Just make sure you allow enough time for the bleach to do its job before you filter it through activated charcoal.  

If I’ve Been Issued a Boil Water Advisory, What Should I Do? 

If it's available to you, the best way to deal with a boil water advisory is to find an alternative source of water. This could be boiled water or water from a friend or neighbor who isn’t under a similar advisory. You also might want to stay at a hotel or order takeout instead of using your water to cook.  

It might also be possible that there’s some clean water available in your house. You may be able to harvest the contents of your hot water heater or melt some ice cubes from your freezer. Of course, you only want to do this if you are sure this water came from before any contamination. If in doubt, sterilize it like you would any other water from your tap.  

If you have no other options, use the sterilization methods from this article or from reputable sources like the EPA.  

Check out our article on boil water advisories to learn more tips including what to do after the notice is lifted.