Authorities may issue a boil order if there is a question about the healthfulness of the water supply. This may be due to water tests that show the presence of coliform bacteria or conditions that could cause a health concern about the water supply.
Under a boil order, drinking water from the public water system should be purified. The Red Cross indicates the safest method is to boil water vigorously for 3 to 5 minutes (5 minutes at higher altitudes). They also indicate adding 16 drops of liquid bleach per gallon can disinfect the water. Stir and let stand for 30 minutes. If the water does not have a slight bleach odor, repeat the dosage and let stand for another 15 minutes. If you still have power, refrigerate the water after you have boiled it.