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Water Abroad
Treatment of Water to Make it Safe for Drinking
In areas where tap water is not chlorinated or where
sanitation is poor, there are several alternative
methods for ensuring water is safe to drink. These
include boiling the water, chemically disinfecting
it, filtering it, using various combinations of the
previously stated methods, or buying bottled water.
Remember: if the tap water is not safe to drink in
the area you are visiting, do not use it to
reconstitute juice or to rinse fresh fruits and
vegetables. Also avoid ice made from tap water.
Below we describe ways to make sure water is safe to
drink.
Bottled Water
Bottled water from a trusted source is a recommended
alternative to tap water. Before drinking, be sure
all bottled beverages have fully sealed caps. If
seals are not intact, the bottles may have been
refilled.
Boiling Water
Boiling water is the best method for making water
safe to drink. Boiling water as recommended will
kill bacterial, parasitic, and viral causes of
diarrhoea. Adding a pinch of salt to each quart will
improve the taste.
Directions for Boiling Water
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Boil water vigorously for 1 minute and allow it to
cool to room temperature (do not add ice).
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At altitudes greater than 6,562 feet (>2,000 m),
boil water for 3 minutes or use chemical
disinfection after water has been boiled for 1
minute.
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Chemical Disinfection
If boiling water is not possible, chemical
disinfection with iodine (e.g., Globaline,
Potable-Aqua, or Coghlan’s, found in pharmacies
and sporting goods stores) is another method for
making water safer to drink. Cryptosporidium (a
parasite that can cause diarrhoea) and other
coccidian parasites (e.g., Cyclospora,
Toxoplasma) might not be killed by this method.
Cloudy water should be strained through a clean
cloth into a container to remove any sediment or
floating matter, and then the water should be
treated with iodine.
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Directions for disinfecting water with iodine
Iodine
tablets
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Follow the tablet manufacturers' instructions.
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If water is cloudy, double the number of tablets.
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If water is extremely cold, less than 5° C (41°
F), an attempt should be made to warm the water,
and the recommended contact time (standing time
between adding a chemical disinfectant to the
water and drinking the water) should be increased
to achieve reliable disinfection.
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Note:
Be sure the tablet size is correct for a Litre
of water. |
Tincture of Iodine
- measure out your dose to water.
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If
using tincture of iodine 2% solution, add 5 drops to
a Litre or Quart of clear water. If the water is
cloudy, add 10 drops per Litre or Quart. (Note: 20
drops=1 ml.)
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Allow
the water to stand for 30 minutes before drinking
when the water temperature is at least 25°C (77°F).
Increase the standing time for colder water: (e.g.,
for each 10° less than 25°C (77°F), allow the water
to stand for double the time before drinking it.
Crystalline Iodine
(found at some chemical companies and sporting goods
stores)
First
make a saturated solution and then measure your own
dose to add to water. The crystalline form stores
well indefinitely and new batches of the saturated
solution can be made from a small amount of crystals
each time you take a trip.
To
prepare a stock of Crystalline Iodine saturated
solution:
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Place
4-8 grams of crystalline iodine into a 1-2 oz
container and fill with water. Note: 1oz=6
teaspoons. Warning: crystalline iodine at 4-8 grams
is a lethal dose if accidentally swallowed in a
single dose. Keep out of the reach of children.
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Shake
the bottle vigorously for 1 minute. Allow several
additional minutes for the iodine to maximally
dissolve in the available water. Some crystals
should always be visible; if they totally dissolve,
then more crystals should be added to the container
to insure that iodine saturation of the stock
solution has been achieved.
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If the
water to be treated is clear, add 13 ml of saturated
iodine solution -- liquid above the crystals, not
the crystals themselves -- per Litre or Quart. Note:
5 ml= 1 teaspoon. 13 ml = about 2.5 teaspoons.
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In
cloudy water, add 26 ml of saturated solution per
Litre or Quart. Note: Allow the solution to stand 20
minutes before drinking the disinfected water when
the water temperature is 20-25°C (68-77°F). Increase
the standing time with colder water. For each 10°
less than 25°C (77°F), allow the water to stand for
double the time before drinking.
Portable Water Filters
Certain types of portable water filters can also
remove some types of infectious agents from drinking
water. However, most of the portable filters on the
market do not effectively remove viruses, thus
chemical disinfection of water is needed after
filtering with such filters to make the water safer
for drinking. Some portable water filters designed
to remove parasites (Giardia/Cryptosporidium) have
an "absolute” pore sizes of 0.1 to 1-micrometer and,
therefore, may also remove most diarrhoea-causing
bacteria. See the Division of Parasitic Diseases'
Guide to Water Filters and Bottled Water to learn
about different filters and those that filter
Cryptosporidium. Viruses are smaller than 0.1 micron
and will NOT be removed by filters with a pore size
of 0.1 or larger. To kill viruses that may pass
through these filters, add iodine (as described
above) to the filtered water before you drink it.
Note:
Chlorine in various forms has also been used for
chemical disinfection. However, it is not as
reliable as iodine for killing disease causing
organisms in the wide range of water-quality
conditions that travellers might encounter.
Warnings
Crystalline iodine 4-8 grams used in a stock
solution constitutes a human lethal dose if
accidentally swallowed in a single dose. Keep out of
the reach of children.
Water that has been disinfected with iodine is NOT
recommended for pregnant women, people with thyroid
problems, those with known hypersensitivity to
iodine, or continuous use for more than a few weeks
at a time.
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