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Here we provide the details of the amount of different types of disinfectant needed to treat drinking water - the disinfectant concentration needed to make water safe to drink. We explain the increased treatment time or contact time needed depending on the water temperature and depending on whether or not the treated water is cloudy. This article series outlines methods to purify or sanitize drinking water in an emergency following a disaster such as an earthquake, flood, or hurricane. A companion article, DRINKING WATER - EMERGENCY SOURCES,describes possible sources of drinking water that may be useful in emergency conditions.

Flood Response Checklist lists key actions you should take after building flooding to minimize mold damage, and includes some safety warnings. Before entering a building that has been affected by a disaster such as fire, earthquake, or flood, See BUILDING ENTRY PROCEDURE for some safety warnings for occupants, building owners, or volunteers who may find themselves indoors in a disaster area and without immediate assistance from rescue workers or other experts.

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How Much Disinfectant to Use in Drinking Water?

The amount of disinfectant needed to purify water depends on how contaminated the water is to begin with. If you are using liquid iodine and have no better authoritative information, try a teaspoon of iodine per gallon of water. Other experts recommend:

• Iodine in clear water: 5 drops of 2% tincture of iodine per quart of clear water
• Iodine in cloudy water: 10 drops of 2% tincture of iodine per quart of cloudy water
• Other water disinfectant products based on iodine: the label will indicate the number of capfuls of disinfectant to use per quart of water
• Iodine tablets, such as PotableAqua™ - (50 tablets per bottle) two tablets treats a quart of water and are effective against Giardia lambia.
• Bleach for sterilizing drinking water: the number of drops of bleach to add per gallon of water depend on the percent concentration of the bleach product you are using. Let your bleached water stand for 30 minutes before using it. If the water does not have a slight "bleach" smell, repeat the dose and let the water stand for an additional 15 minutes. If you let the water stand longer the unpleasant bleach odor will dissipate completely.
  • 1% bleach: use 40 drops of bleach per gallon of drinking water
  • 2% to 6% bleach solution: use 8 drops of bleach per gallon of water
  • 7% to 10% bleach solution: use 4 drops of bleach per gallon of water
  • Unknown bleach concentration (presuming this is store-bought laundry bleach): use 10 drops of bleach per gallon of water.

Wait Time & Water Temperature when adding a disinfectant, before drinking water

• Typical wait time before drinking treated water is at least 30 minutes from the time that the treatment tablet has become fully dissolved in the water. The necessary time could be longer.
• Water temperature should be 65 degF or higher before treatment with bleach for best results. You may be able to warm your water by placing it in the sun. If the water is below 40 deg.F. you should double the wait time before consuming it.
• Water temperature should be 68 degF or higher before treating it with iodine. Iodine is more effective than bleach in killing off Giardia contamination in water.
• Be sure to read the instructions. Iodine, bleach (sodium hypochlorite), or other water disinfectants will require some wait time to permit the chemical to act on water bacteria before the water can be consumed.
• Using any chemical to sterilize water will require sufficient contact time between the chemical and the water before the water can be consumed.
• The chemical, bleach, or iodine, needs time to kill the microorganisms in the water.
• If you have iodine tablets intended for purifying water, the tablet bottle label should indicate the number of tablets to use per gallon of water and also the length of time that you must let the water sit before drinking it.
• If using liquid iodine to purify water, let the treated water sit for a day before using it to drink.
• If your water supply is very cold you will need to increase the wait time for the chemical disinfectant to act before the water can be consumed.
• If your water supply is cloudy you will need to increase the wait time for the chemical disinfectant to act before the water can be consumed. That's why experts recommend filtering the water with a clean cloth first if you can. In an emergency you might also be able to use clean coffee filters or even plain white paper towels.

Links provided just below continue with details about various methods to disinfect or purify emergency drinking water.

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Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY
FLOODS & MOLD CLEAN/PREVENT A Guide to Dealing with Flood Damage & Mold Prevention &r Cleanup of Flooded Homes
  FIRST PRIORITIES When Responding to a Flooded Building
  BUILDING ENTRY PROCEDURE How to Enter a Building After a Building Flood
  DRINKING WATER - EMERGENCY PURIFICATION How to purify emergency drinking water, how to remove odors
    How to Purify Water
    Boiling Water for Drinking
    Iodine Tablets or Iodine Disinfectant
    Bleach as a Disinfectant for Drinking Water
    Vegetable Disinfection Washes
    Hydrogen Peroxide for Water Disinfection
    Vinegar & Other Disinfectants
    How Much Disinfectant to Use
    Wait Time & Water Temperature
    Filters for Drinking Water Purification
    Giardia in Drinking Water
  DRINKING WATER - EMERGENCY SOURCES Where to find drinking water in an emergency
  ELECTRICAL SAFETY for Flood Damage Inspectors
  FLOOD DAMAGE TO FOUNDATIONS
  FLOOD RESPONSE CHECKLIST Checklist of Key Steps to Minimize Mold Damage After a Building Flood
  INEFFECTIVE MOLD PRODUCTS Ineffective Mold Products and Procedures to Avoid in Mold Cleanup/Prevention
  FURTHER STEPS PREVENT MOLD Further Steps to Avoid Mold Damage After a Building Flood
  WHEN TO STOP LOOKING FOR MOLD after Flooding: When is a Mold Cleanup Job Complete?
  GENERAL MOLD PREVENTION Preventing Future Mold After a Flooded Building Cleanup
  FLOOD DAMAGE RFERENCES References on Mold Prevention and Flood Damage
  FLOOD VENTS How to Use Flood Vents for Structural Protection from Flooding - Flood Venting in Foundations and Enclosures Below Design Flood Elevation
  SEPTIC SYSTEMS & FLOODS What to Do after a Flood - Septic Flood Response, Safety, Health, Maintenance, Repair Advice
  SEWAGE CONTAMINATION IN BUILDINGS how to detect and respond to sewage backups
  SEWAGE PATHOGENS in SEPTIC SLUDGE what are the contaminants in sewage
  Wind Damage to Roofs how to assess and identify wind damage to roofs
PLUMBING TOPICS
WATER TREATMENT EQUIPMENT CHOICES
WELL CHLORINATION SHOCKING PROCEDURE

• Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. (727) 595-4211 mark@BestTampaInspector.com 11/06
• Hankey and Brown home inspectors, Eden Prairie, MN, technical review by Roger Hankey, prior chairman, Standards Committee, American Society of Home Inspectors - ASHI. 952 829-0044 - hankeyandbrown.com 11/06
• Dr. Omar Amin, of the Tempe AZ Parasitology Center, corresponded with one of our readers asking about peroxide: "You can use hydrogen peroxide if you want to but we do not have a track record of percentage dilution". Dr. Amin has done research for the US military and for the CDC.
• Potable Aqua® emergency drinking water germicidal tablets are produced by the Wisconsin Pharmacal Co., Jackson WI 53037. 800-558-6614 pharmacalway.com
• Aquamira™ chlorine dioxide water purification kits - see www.aquamira.com/
  "Aquamira Water Treatment Drops were introduced to the Outdoor market in 1999 and have been a favorite of top outdoor guides and instructors ever since. Whether you are camping, traveling in a foreign country or faced with a disaster, our goal is to provide you with safe, pure and good tasting drinking water. Our complete line of water treatment products include leading edge purification and filtration technologies developed and tested in the lab and proven in the field. We offer systems and products that will provide water for a single individual or a village and almost anything in between."
  
• Katadyn™, a Swiss corporation provides water filters, desalinization equipment, and their Micropur chlorine dioxide water purification - see www.katadyn.com/usen/
  "Katadyn offers a wide variety of water filtration and purification products suitable for any need. This allows outdoor enthusiasts and travelers to take along products for making their own drinking water when preparing their trips."
• Arlene Puentes, a licensed home inspector, educator, and building failures researcher in Kingston, NY. 11/29/06
• Wilderness Medical Society has advice about boiling water for consumption
• Princeton University - www.princeton.edu
• "Bacteria in Drinking Water" - "Chlorine," Karen Mancl, water quality specialist, Agricultural Engineering, Ohio State University Extension. Mancl explains factors affecting the effectiveness of chlorine in water as a means to destroy bacteria and other microorganisms. OSU reports as follows:

  Chlorine kills bacteria, including disease-causing organisms and the nuisance organism, iron bacteria. However, low levels of chlorine, normally used to disinfect water, are not an effective treatment for giardia cysts. A chlorine level of over 10 mg/1 must be maintained for at least 30 minutes to kill giardia cysts. -- http://ohioline.osu.edu/b795/index.html is the front page of this bulletin.

• Crystal Clear Supply provides portable ceramic water filter purifiers and portable reverse osmosis water treatment equipment - see http://www.crystalclearsupply.com/category_s/7.htm
• "Do Iodine Water Purification Tablets Provide an Effective Barrier against Cryptosporidium parvum?", Starke, Jeffrey A., Bowman, Dwight D., Labare, Michael, Fogarty, Elizabeth A., and others, Military Medicine, 25 October 2001 [possibly a later version of this article appeared in 2005 -DF] http://www.amsus.org/military medicine/milmed.htm
• "Drinking Water Safety in Emergencies", University of Minnesota extension, extension.umn.edu/info-u/nutrition/BJ646.html
• FDA Warning about drinking hydrogen peroxide: www.truthorfiction.com/rumors/h/hydrogen-peroxide.htm This article cites a 2003 entry in Journal of Food and Science on using Hy.Perox to sterilize vegetables, referring to E.coli - NOT to Giardia.
• www.epa.gov/ogwdw/mdbp/pdf/alter/chapt_2.pdf provides an article on use of disinfectants for water treatmen
• This patent application for UV light sterilization www.patentstorm.us/patents/6565803.html Lists good references on water purification for Giardia et als
• Giardia exposure limits for drinking water: see www.mass.gov/dep/water/drinking/standards/giardia.htm is the current regulatory exposure limit (your minimum target for sterilization)
• Wikipedia on history of use of hydrogen peroxide: Information on Hydrogen peroxide as a sterilant is in Wikipedia at en.wikipedia.org/wiki/Sterilization_(microbiology) HO2 has been used for a long time, including by vaporization for sterilizing freeze dryers.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• Potable Aqua® emergency drinking water germicidal tablets are produced by the Wisconsin Pharmacal Co., Jackson WI 53037. 800-558-6614 pharmacalway.com
• Principles and Practice of Disinfection, Preservation and Sterilization (Hardcover)
  by A. D. Russell (Editor), W. B. Hugo (Editor), G. A. J. Ayliffe (Editor), Blackwell Science, 2004. ISBN-10: 1405101997, ISBN-13: 978-1405101998.
  "This superb book is the best of its kind available and one that will undoubtedly be useful, if not essential, to workers in a variety of industries. Thirty-one distinguished specialists deal comprehensively with the subject matter indicated by the title ... The book is produced with care, is very readable with useful selected references at the end of each chapter and an excellent index. It is an essential source book for everyone interested in this field. For pharmacy undergraduates, it will complement the excellent text on pharmaceutical microbiology by two of the present editors."
  The Pharmaceutical Journal: "This is an excellent book. It deals comprehensively and authoritatively with its subject with contributions from 31 distinguished specialists. There is a great deal to interest all those involved in hospital infection ... This book is exceptionally well laid out. There are well chosen references for each chapter and an excellent index. It is highly recommended." The Journal of Hospital Infection.: "The editors and authors must be congratulated for this excellent treatise on nonantibiotic antimicrobial measures in hospitals and industry ... The publication is highly recommended to hospital and research personnel, especially to clinical microbiologists, infection-control and environmental-safety specialists, pharmacists, and dieticians."
  New England Journal of Medicine: City Hospital, Birmingham, UK. Covers the many methods of the elimination or prevention of microbial growth. Provides an historical overview, descriptions of the types of antimicrobial agents, factors affecting efficacy, evaluation methods, and types of resistance. Features sterilization methods, and more. Previous edition: c1999. DNLM: Sterilization--methods.
• Handbook of Disinfectants and Antiseptics, Joseph M. Ascenzi (Editor), CRC, 1995, ISBN-10: 0824795245 ISBN-13: 978-0824795245 "The evaluation of chemical germicides predates the golden age of microbiology..." -
  This well-focused, up-to-date reference details the current medical uses of antiseptics and disinfectants -- particularly in the control of hospital-acquired infections -- presenting methods for evaluating products to obtain regulatory approval and examining chemical, physical, and microbiological properties as well as the toxicology of the most widely used commercial chemicals.
• When Technology Fails, Matthew Stein, Chelsea Green Publisher, 2008,493 pages. ISBN-10: 1933392452 ISBN-13: 978-1933392455, "... how to find and sterilize water in the face of utility failure, as well as practical information for dealing with water-quality issues even when the public tap water is still flowing". Mr. Stein's website is www.whentechfails.com/

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