Making Water Safe in an Emergency
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Making Water Safe in an Emergency cdc.gov/healthywater/emergency/drinking/making-water-safe.html If you don't have safe bottled water and if boiling is not possible, you often can make small quantities of filtered and settled water safer to drink by using a chemical disinfectant such as unscented household chlorine bleach. Disinfectants can kill most harmful or disease-causing viruses and bacteria, but are not as effective in controlling more resistant organisms, such as the parasites Cryptosporidium and Giardia.(https://www.cdc.gov/parasites/giardia/index.html) Chlorine dioxide tablets can be effective against Cryptosporidium if the manufacturer’s instructions are followed correctly. To disinfect water with unscented household liquid chlorine bleach: If the water is cloudy, 1. Filter it through a clean cloth, paper towel, or coffee filter OR allow it to settle. 2. Draw off the clear water. 3. Follow the instructions for disinfecting drinking water that are written on the label of the bleach. 4. If the necessary instructions are not given, check the "Active Ingredient" part of the label to find the sodium hypochlorite percentage, and use the information in the following table as a guide. Typically, unscented household liquid chlorine bleach will be 8.25% sodium hypochlorite, though concentrations can be different. Using the table below, add the appropriate amount of bleach using a medicine dropper, teaspoon, or metric measure (milliliters). 5. Stir the mixture well. 6. Let it stand for at least 30 minutes before you use it. 7. Store the disinfected water in clean, sanitized containers(https://www.cdc.gov/healthywater/emergency/drinking/cleaning-preparing-storage- containers.html) with tight covers. If the water is clear, 1. Follow the instructions for disinfecting drinking water that are written on the label of the bleach. 2. If the necessary instructions are not given, check the "Active Ingredient" part of the label to find the sodium hypochlorite percentage, and use the information in the following table as a guide. Typically, unscented household liquid chlorine bleach will be 8.25% sodium hypochlorite, though concentrations can be different. Using the table below, add the appropriate amount of bleach using a medicine dropper, teaspoon, or metric measure (milliliters). 3. Stir the mixture well. 4. Let it stand for at least 30 minutes before you use it. 5. Store the disinfected water in clean, sanitized containers(https://www.cdc.gov/healthywater/emergency/drinking/cleaning-preparing-storage- containers.html) with tight covers. 1/3 Making water safe to use with bleach having a 1% concentration of sodium hypochlorite * If the water is cloudy, murky, colored, or very cold, add double the amount of bleach listed below 1 quart/liter water 1 gallon water 5 gallons water If you have a dropper: If you have a dropper: If you have a dropper: Add 10 drops of bleach Add 40 drops of bleach Add 200 drops of bleach If you have something that If you have something that If you have something that measures milliliters (ml): measures milliliters (ml): measures milliliters (ml): Add ½ ml of bleach Add 2½ ml of bleach Add 12½ ml of bleach If you have a measuring spoon: If you have a measuring spoon: If you have a measuring spoon: Add ⅛ teaspoon of bleach Add ½ teaspoon of bleach Add 2½ teaspoons of bleach Making water safe to use with bleach having a 4-6% concentration of sodium hypochlorite * If the water is cloudy, murky, colored, or very cold, add double the amount of bleach listed below 1 quart/liter water 1 gallon water 5 gallons water If you have a dropper: If you have a dropper: If you have a dropper: Add 2 drops of bleach Add 8 drops of bleach Add 40 drops of bleach If you have something that If you have something that If you have something that measures milliliters (ml): measures milliliters (ml): measures milliliters (ml): Add 0.1 ml of bleach Add ½ ml of bleach Add 2½ ml of bleach If you have a measuring spoon: If you have a measuring spoon: If you have a measuring spoon: Amount too small to measure Amount too small to measure Add ½ teaspoon of bleach Making water safe to use with bleach having an 8.25% concentration of sodium hypochlorite** * If the water is cloudy, murky, colored, or very cold, add double the amount of bleach listed below 1 quart/liter water 1 gallon water 5 gallons water If you have a dropper: If you have a dropper: If you have a dropper: Add 2 drops of bleach Add 6 drops of bleach Add 30 drops of bleach If you have something that If you have something that If you have something that measures milliliters (ml): measures milliliters (ml): measures milliliters (ml): Amount too small to measure Add ½ ml of bleach Add 2 ml of bleach 2/3 1 quart/liter water 1 gallon water 5 gallons water If you have a measuring spoon: If you have a measuring spoon: If you have a measuring spoon: Amount too small to measure Amount too small to measure Add ⅓ teaspoons of bleach **8.25% is the most common household bleach concentration available Making water safe to use with bleach having an unknown concentration of sodium hypochlorite * If the water is cloudy, murky, colored, or very cold, add double the amount of bleach listed below 1 quart/liter water 1 gallon water 5 gallons water If you have a dropper: If you have a dropper: If you have a dropper: Add 10 drops of bleach Add 40 drops of bleach Add 200 drops of bleach If you have something that If you have something that If you have something that measures milliliters (ml): measures milliliters (ml): measures milliliters (ml): Add ½ ml of bleach Add 2½ ml of bleach Add 12½ ml of bleach If you have a measuring spoon: If you have a measuring spoon: If you have a measuring spoon: Add ⅛ teaspoon of bleach Add ½ teaspoon of bleach Add 2½ teaspoons of bleach To disinfect water with tablets that contain chlorine or iodine: Follow the manufacturer’s instructions on the label or in the package. Chlorine dioxide tablets can be effective against Cryptosporidium if the manufacturer’s instructions are followed correctly. Iodine and iodine-containing tablets (tetraglycine hydroperiodide) or chlorine tablets are not effective against Cryptosporidium. 3/3 EMERGENCY DISINFECTION OF DRINKING WATER In an emergency situation where regular water service has been interrupted – like a hurricane, flood, or water pipe breakage – local authorities may recommend using only bottled water, boiled water, or disinfected water until regular water service is restored. The instructions below show you how to boil and disinfect water to kill most disease-causing microorganisms that may be present in the water. However, boiling or disinfection will not destroy other contaminants, such as heavy metals, salts, and most other chemicals. ONLY USE WATER THAT HAS BEEN PROPERLY DISINFECTED FOR DRINKING, COOKING, MAKING ANY PREPARED DRINK, WASHING DISHES, AND FOR BRUSHING TEETH. Use bottled water or water you have properly prepared and stored as an emergency water supply. Boil water, if you do not have bottled water. Boiling is sufficient to kill pathogenic bacteria, viruses and protozoa (WHO, 2015). − If water is cloudy, let it settle and filter it through a clean cloth, paper towel, or coffee filter. − Bring water to a rolling boil for at least one minute. At altitudes above 5,000 feet (1,000 meters), boil water for three minutes. − Let water cool naturally and store it in clean containers with covers. − To improve the flat taste of boiled water, add one pinch of salt to each quart or liter of water, or pour the water from one clean container to another several times. Disinfect water using household bleach, if you can’t boil water. Only use regular, unscented chlorine bleach products that are suitable for disinfection and sanitation as indicated on the label. Do not use scented, color safe, or bleaches with added cleaners. − If water is cloudy, let it settle and filter it through a clean cloth, paper towel, or coffee filter. − Locate a clean dropper from your medicine cabinet or emergency supply kit. − Locate a fresh liquid chlorine bleach or liquid chlorine bleach that is stored at room temperatures for less than one year. The label should say that it contains 8.25% of sodium hypochlorite. − Use the table on the next page as a guide to decide should add to the water, for example, add 6 drops of bleach to each gallon of water. Double the amount of bleach if the water is cloudy, colored, or very cold. − Stir and let stand for 30 minutes. The water should have a slight chlorine odor. If it doesn’t, repeat the dosage and let stand for another 15 minutes before use. − If the chlorine taste is too strong, pour the water from one clean container to another and let it stand for a few hours before use. Table 1: Bleach to Water Dose Guidance OTHER DISINFECTION METHODS Amount of Liquid Bleach If you don’t have liquid bleach, you can use one of the Volume of Water to Add† other disinfection methods described below. 1 quart/liter 2 drops • Granular calciuM hypochlorite. The first step is to 1 gallon 6 drops make a chlorine solution that you will use to 2 gallons 12 drops (1/8 teaspoon) disinfect your water. For your safety, do it in a 4 gallons 1/4 teaspoon ventilated area and wear eye protection. Add one 8 gallons 1/2 teaspoon heaping teaspoon (approximately ¼ ounce) of † Bleach contains 8.25% sodium hypochlorite. high-test granular calcium hypochlorite (HTH) to ADDITIONAL WATER GUIDANCE FOR EMERGENCIES two gallons of water and stir until the particles have dissolved.