The WAPI (Water Pasteurization Indicator) is a reusable, inexpensive thermometer employing a plug of soybean wax which melts at 68˚C, just above the 65˚C or 149˚F pasteurization temperature for water or milk, at which point all disease-causing organisms (bacteria, viruses, and parasites) are killed.
I prefer pasteurization over boiling because it requires less fuel to heat the water. I also appreciate that it takes less time. I am rather absent-minded, sometimes water has boiled away before I realize it. Water that has boiled down has a higher concentration of minerals and chemical pollutants in it.
I like the cleverness of this design, but I don’t think I need this item as long as I have a thermometer.
The following is from http://solarcooking.wikia.com/wiki/WAPI_production:
The Monterey Peninsula Rotary Club now has WAPI kits available in which stainless steel wire replaces the monofiliment fishing line and is good for all applications including Open flame fires, which had the tendency to melt the traditional fishing line. The Kit contains all the components and instructions to build 200 WAPIs. These are reusable and virtually indestructable.
The cost is $85 (about $.42 each) plus shipping. If you are interested in a fun project that teaches about the perils of unclean water and then show folks how to make a difference, contact us at WAPI@pacbell.net. This is a great fellowship project for Rotary Clubs, Rotary Interact Clubs, Church youth groups, etc..
New Improved Super WAPI – now with stainless steel wires and brass end caps that are an improvement over the older fishing line version.
The Reusable WAPI – Water Pasteurization Indicator. A small polycarbonate tube contains a wax that melts when water is heated enough to be pasteurized (65°C/149°F). The wax changes state and falls to the bottom of the tube, This is an extremely useful, pocket sized, reusable device that should be in every campers kit and every home emergency kit. It is just 1.5 inches long and about the diameter of a pencil, and weighs about 5 grams.
Disease-causing micro organisms in water are killed by exposure to heat in a process known as pasteurization. Water heated to 65 C (149 F) for a short period of time is free from microbes, including E. coli, Rotaviruses, Giardia and the Hepatitis A virus. (Milk and other Foods require 71 C (160 F) ). The
This is an effective way to get safe drinking water without boiling.
Reference Temperatures: :
Worms, Protozoa cysts (Giardia, Cryptosporidium, Entamoeba) are killed rapidly at 55°C (131°F)
Bacteria (V. cholerae, E. coli, Shigella, Salmonella typhi), and Rotavirus are killed rapidly at 60°C (140°F)
Hepatitis A virus is killed rapidly at 65°C (149°F)
Water Boils at 100°C (212°F)
The following is portions of a July 4th, 2011 article at http://www.livestrong.com/article/484769-benefits-of-drinking-boiled-water:
….Boiling water also releases dissolved gases that give drinking water flavor, so your boiled drink may taste flat. A flat taste could be better or worse than the original taste, depending on your drinking water’s quality.
If you must drink from a biologically contaminated water source, boiling kills 100 percent of the dangerous pathogens in your drinking water. Experts disagree on how long to boil drinking water, as heating to temperatures below boiling also kills most bacteria and viruses. If you heat water to only 165 degrees Fahrenheit for 30 minutes, you kill most organisms in the water. Because your water could contain spores of heat-resistant pathogens such as cryptosporidium, the Centers for Disease Control and Prevention recommends bringing the water to a rolling boil for one minute…
Boiling water forces out dissolved gases. Oxygen and carbon dioxide in water give the liquid a pleasant flavor, but gases formed as byproducts of decomposition cause unpleasant smells and tastes. If your original drinking water smells or tastes bad, boiling water often improves the water quality. You can restore flavor by pouring water back and forth between containers several times, mixing oxygen and carbon dioxide back into it. Boiling helps preserve safe drinking water, but you must sterilize the storage container, as well. The same canning methods used for long-term preservation of acidic foods also work for boiled water. Boiled water in sealed mason jars heated in a boiling water bath can store safely for years.
Dissolved minerals could give your water a bad taste. If you boil hard water, some dissolved minerals precipitate out, forming a hard layer on the inside of the container used. Two classes of mineral salts cause hard water problems: calcium and magnesium, as carbonates, bicarbonates and hydroxides form a hard mineral layer that accumulates inside containers used for boiling drinking water. Magnesium and calcium sulfates and chlorides cause permanent water hardness. If your water’s off taste comes from these mineral salts, boiling only concentrates the solution by evaporating some of the water and leaving the dissolved salts behind.
Boiling reduces the volume of some chemical contaminants such as benzene and toulene, which boil at a lower temperature than water. Boiling does not always reduce chemical pollution….
This is one of many well-written articles on water safety and other subjects at Livestrong.com.
The following is from http://www.appropedia.org/WAPI_%28Water_Pasteurization_Indicator%29:
The hydrogenated soybean oil called Myverol 18-06 K (a food-grade emulsifier powdered wax) is encased in a small clear plastic tube, weighted with a metal washer. Fishing line or wire suspends the WAPI toward the bottom of the water container (where the water is coolest). The WAPI is oriented with the wax plug at its top, but after melting the wax flows to the bottom part. Then the user can remove the WAPI by the string or wire without contaminating the clean water with the fingers.
For directions for making a WAPI from a ballpoint pen, visit http://solarcooking.org/phpBB2/viewtopic.php?p=82&sid=ef8dae20a4e79b4fa8fd4ceacdc08755.