Potable water is water that is considered safe to drink. Tap water has usually been treated by the local municipality to make it potable, but there are times when the supply has been contaminated and you must treat water before using it. Non-potable water is untreated water from lakes, rivers, groundwater, natural springs, and untested ground wells.
The CDC states that "In emergency situations, use bottled water if possible; bottled water is the safest choice for drinking and all other uses," but if you do not have access to bottled water, you can use a variety of methods to treat non-potable water so it is safe to drink, as well as to treat your tap water during a water advisory.
Boil the Water
The most common method of treating water is to boil it. Boiling for sufficient time will kill microbes and may also drive off some toxic chemical contaminants, but others are not affected by boiling.
What Are Toxic Chemical Contaminants?
Some chemical contaminants that can be found in water include lead and other metals, pesticides and fertilizers, drugs, and bleach. These chemicals can be naturally occurring or human-made.
You can use a variety of heating methods to bring the water to a boil. These can include a stovetop burner, microwave, or electric kettle.
- Place the water in a pot or microwave-safe vessel.
- Place the container on the heat source or in the microwave.
- Heat to a rolling boil and keep the water at a rolling boil for 1 minute.
- If microwaving, stir the water to ensure both top and bottom have heated sufficiently.
- Allow the water to cool.
- Pour the water into a clean container for use.
Use Chlorine Bleach
Unscented household bleach can be used to kill bacteria in the water if you aren't able to boil the water. Bleach contains chlorine, which is what is used to make municipal water supplies potable (chlorinated water). If the water is cloudy, you should filter it through a cloth before treating it.
You will need to measure correctly to ensure you use enough bleach, but not too much as it can be poisonous in excess.
- Add 1/8 teaspoon (8 drops) of unscented household bleach to 1 gallon (16 cups) of water.
- Mix the water and bleach well.
- Allow the water to sit for at least 30 minutes before drinking or using it.
Bleach can also be used to sanitize the containers that you will store water in. Make a sanitizing solution of 1 teaspoon of bleach in 1 quart (4 cups) of water. Pour this solution into the container or wipe it inside the container to coat it. Allow it to sit for 30 seconds, then pour out. Allow the container to air dry or rinse it with treated water.
It is important to note that if your water is contaminated with a chemical, disinfectants will not make it drinkable.
Iodine solution, crystals, or tablets are often sold for hikers to easily add to water bottles. Iodine can kill viruses and bacteria and is easy to use (though it is not effective against more resistant organisms like Cryptosporidium). However, it gives the water an aftertaste. Follow the directions provided on the product as the amount used will vary for the solution, crystals, and tablets. Using warm water, if possible.
- Add the iodine to the correct amount of water in your container.
- Mix the iodine well with the water, ensuring some of the solution also coats the lid and threads if using a screwcap bottle.
- Allow the water to sit for 30 minutes after the iodine has fully dissolved before using. If your water is cold (below 40 F), wait 60 minutes before using.
Use a Water Purification Filter
Water purification filters can remove bacteria and protozoans in the water. A carbon filter gets rid of some chemicals and off tastes. Be sure to carefully read the instructions for your water purification filter to use it correctly and to understand what it will and will not remove. You will need to ensure particles in the water do not clog the filter.
- Allow cloudy water to settle for several hours.
- Prefilter the water through a prefilter or cloth.
- Pass the prefiltered water through the water purification filter.
Use an Ultraviolet Light Water Purifier
Ultraviolet (UV) water purification lights can be used to kill bacteria, protozoa, and viruses. Before using this method, filter the water through cloth to remove any solid particles as the light won't be able to sanitize the interior of such particles. It also may not be effective if the water is cloudy. UV lights may be built into water bottles, but one common format is a pen-shaped light powered by batteries.
- Turn the light on and drop it into a container with the water.
- Swish the light around in the water for a couple minutes, according to the manufacturer's instructions.
- Remove the light from the water and use the water.
Use Bottled Water
Commercially bottled water should be safe to use when you don't have access to a potable water supply. Depending on the brand, it may be tap water that has been actively carbon filtered. Some bottled water manufacturers promote their brands as being UV filtered, assuring consumers that bacteria has been removed, or it has been through water distillation or the reverse osmosis process.
- Check the bottled water container for any signs it has been previously opened and refilled.
- Check the expiration date, if present.
- Check the bottle for cracks.
- If you are in doubt, boil or treat the bottled water before using.
When to Call a Professional
There may be occasions when municipal tap water contains higher levels of harmful contaminants like metals, lead, or salt that are not removed by the methods listed. Follow the advice of your local municipality or consult a water technician.
If you live in a rural area with various water sources, you need to make sure your water is safe. Your best option is to consult with a water technician, have your existing tap water analyzed, and then follow their recommendations for making it or keeping it potable.
There are various water filtration systems and products you can buy to help you with this task. Selecting the right one depends on the state of your existing water and what microbes or metals are in it. These filtration systems are much more affordable and easier to install than they used to be and this is the best way to ensure safe water in some areas.
Bleach must never be allowed to mix with ammonia or it will form highly dangerous chlorine gas. Be sure to keep these cleaning supplies separate at all times. Store bleach in a locked cabinet to keep it away from children and pets. Always vent the room well after using bleach. If you are using a camp stove or fire to heat water, do so outdoors to prevent the buildup of dangerous gases indoors.