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Water System Basics
Where does my tap water come from?
Most of your tap water begins as rainfall in the Bull Run Watershed which is near Mt. Hood. A small portion of the water may start as snowfall or fog drip within the watershed. Despite its proximity to the mountain, none of Portland's drinking water originates from Mt. Hood, as the watershed is separated from the mountain by a significant geologic ridge. Some water comes from the city's groundwater supply which the bureau uses as a back-up supply.
How is my tap water treated?
Water runs off in the watershed through streams and rivers into the Bull Run River or Bull Run's reservoirs. From there it goes into the treatment facility in Bull Run where the "raw" water is treated with chlorine to produce drinking water.
Closer to Portland, ammonia is added to the water. Combined with the chlorine, adding ammonia completes a process called chloramination. This simple treatment process ensures that water throughout the water system meets the disinfection requirements of federal and state drinking water regulations.
How does my tap water get to Portland? How does it get to my tap?
Water flows to Portland by gravity. Gravity flow reduces dependence on pumping and its expensive energy needs.
The water travels through distribution mains to all parts of the city. Water mains run beneath sidewalks and streets to individual homes and businesses.
From the water main, a smaller pipe travels to the water meter at each home or business that has water service. The water passes through the meter on its way to your home . The meter measures the amount of water that flows through it. The mains and the water meter are generally owned by the City of Portland.
From the meter, water enters pipes which are the owned by property owner . Those pipes deliver water to your tap.
The City of Portland provides water to nearly one-quarter of the population of Oregon. The city's service area covers Portland residents and the residents of 19 suburban cities and water districts.
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