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Portland Water Bureau

From forest to faucet, we deliver the best drinking water in the world.

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1120 SW Fifth Ave, Suite 600, Portland, OR 97204

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Did You Know...Why a Water Main Breaks?

The Portland Water Bureau’s Maintenance & Construction crews are called out at all hours day and night to repair broken water mains, an average 200 times a year. Most of these repairs involve cast iron and galvanized pipes.  Out of more than 2,100 miles of the city’s water pipe network, there remains about 1,350 miles of cast iron pipe of a variety of ages in the water system. 

100-Year Old Broken Cast Iron Pipe
100-Year Old Broken Cast Iron Pipe

In Portland, cast iron water mains tend to break during the colder times of year, or what our crews call “Main Break Season.”  Colder water can make pipes more brittle. Adding cold air temperatures at or below freezing can cause the ground above a pipe to freeze thereby increasing external stress on a pipe.

Temperature is just one factor. The age of the pipe is another. However, Portland has pipes that are over 100-years old that have not experienced a break. Still, the Water Bureau replaces about five miles of old and vulnerable pipes each year with more durable steel and ductile iron water mains.

Other factors can have an effect on aging pipe. This includes soil conditions, pipe corrosion and ground movement. Disturbances around a water main from work on underground utilities like sewer and natural gas lines as well as road construction can cause an old main to weaken over time and later break. 

Our Maintenance & Construction crews say it usually takes about a week following a cold snap before they start seeing main breaks. 

Crews excavate site to get to pipe
Crews excavate site to get to pipe

On October 29th, there was a major main break of a 24-inch diameter, 100-year old pipe on W Burnside Street at SW 4th Avenue. Since November 27th, our crews have repaired five main breaks, which is the highest concentration the bureau has seen this year. On December 1st, our crews responded to a break on NE 92nd Avenue, near NE Hill Way. It was an 8-inch diameter cast iron pipe that had been in the ground just 62 years.

Some main breaks cause major street repairs
Some main breaks cause major street repairs

When the Portland Water Bureau is repairing a main break, please remember we appreciate the patience and understanding of customers and motorists affected by the temporary water service shutdown and street closure.

Tim Hall
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