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Portland Water Bureau

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Why Utilities Have to Issue Boil Water Advisories

By Teresa Black 0 Comments

The recent Boil Water Advisory issued by the City ofTigard has prompted some insightful questions from the public. What causes a Boil Water Advisory to be issued?

Boil Water Advisories are required by state and federal regulations for a variety of reasons to ensure public health protection. Often, the reason for an advisory is due to the detection of bacteria within the drinking water system. Although drinking water is disinfected at the source to address any bacteria and most other microbial contaminants that may be present, these contaminants can sometimes be reintroduced into treated water as it moves through pipes, tanks and reservoirs and on to customers’ taps.   

Contamination can occur when there is a loss of water pressure, a pipe breaks, or another event occurs that exposes drinking water to outside elements.  For example, a broken water pipe might allow for stormwater containing bacteria to be introduced into pipes downstream of the break. Utilities try to find out the precise cause whenever there is a detection; however, it is not always possible to make an exact determination.

Until follow-up testing confirms that no bacteria or other contaminants are present in the drinking water system, customers in an affected area can ensure the safety of their drinking water by boiling it according to the directions provided by their utility.

For more information on the regulations governing Boil Water Advisories, go to

Edward Campbell

PortlandWater Bureau


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