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Maintaining water quality with hydrant flushing

Three photos of different flushing techniques. First is water flowing out of an orange hydrant and gently splashing on the curb and street with a blue sign behind saying "flushing our system to maintain water quality". The middle photo has a woman opening a valve on a hydrant that has a hose connected to it and water is spraying out the end of the hose. The last photo is of a orange hydrant that has a red box - the autoflusher - attached to the side and water is splashing out the bottom of the box.
When we need to clean inside the city’s pipes, we flush water through hydrants. It’s one way we maintain excellent water quality.
On this page

About hydrant flushing

Hydrant flushing is a technique used across the country to maintain water quality and clean the pipes that deliver water to homes and businesses. In unfiltered water systems, such as Portland’s, sediment and other organic material accumulate at the bottom of the water mains. This material can impact water quality and cause discolored water at the tap if it is stirred up. (Events that could stir up that material include construction, firefighting, and main breaks.) When we flush hydrants, we flush the material out and bring fresh water into the mains.

Water used during flushing is doing important work. While it may look wasteful, the flushing technique we use is an efficient and necessary use of water to maintain the integrity of the pipes and ensure excellent water quality. Similar to how we brush our teeth every day, the Water Bureau cleans the inside of our water mains on a routine basis. It’s an essential part of, and a planned investment in, maintaining the health of our water system.

Environmental Technician Mikkel Holt explains the work him and his crews do to flush the water mains and hydrants from the system.

Using hydrant flushing, we are currently on track to clean the city’s 2,200 miles of water mains before the new water filtration plant is online in 2027. We want to flush all the mains before then to help prepare the system for a change in water quality and chemistry once the filtration plant is running. After the filtration plant is online, we’ll keep flushing on a continual basis to maintain water quality and drinking water infrastructure.

Our flushing team uses three types of flushing to clean the water main or maintain water quality in an area: autoflushing, spot flushing, and unidirectional flushing.

Flushing happening now

Find out where is flushing happening in the City on our WaterWorks map

Photo of an orange hydrant with a red box, an autoflusher, attached to it. Next to the hydrant is a white sign that says: Flushing our system to maintain water quality. Water may discharge without warning.
Autoflushers look like red boxes attached to hydrants. The mechanism inside the box is programed to turn on for specific amounts of time. The autoflushers are installed in specific areas to maintain water quality in those neighborhoods.

Flushing usually doesn’t affect Portlanders as they’re going about their day. If you see flushing crews working in your area, please drive carefully and treat them like any other road construction crew.

Flushing crews usually work Monday through Friday, between 8:00 am and 4:00 pm. Every once in a while, circumstances call for crews to work outside these hours.

If there is an autoflusher installed in your neighborhood, they typically run during the night. If you see an autoflusher running during the day, report it by calling 503-823-7525. If you leave a message, please include the intersection where the hydrant and autoflusher are located.

What to expect

Typical flushing activities

Worker wearing a bright yellow safety vest who is turning a chest-high tool that is in a hole in the street.

Crews will be working in the street and at hydrants. You may see them accessing valves in the street to change how water flows through the pipe.

Some crews turn hydrants on at a slow flow and leave the hydrant running and unattended for several hours. The crews will come back and turn off the hydrant later.

Crews doing planned flushing work attach large hoses to hydrants and turn on the hydrant at a fast flow. There will be water spraying from the hose and water could pool in the road. Crews clear storm drains to minimize water pooling. Crews do not leave hydrants unattended during this type of flushing. This type of flushing lasts less than an hour.

Safety during flushing

Photo of a woman wearing a yellow safety vest next to an orange hydrant that has water flowing out of it. The woman is writing notes on a metal clipboard.
Water Bureau crews use spot flushing as needed to address water quality issues or concerns reported by residents. Crews also use spot flushing proactively to maintain water quality in neighborhoods. Hydrants used for spot flushing may be left on and unattended for a few hours while the flushing is happening.

If you see flushing crews working in your area, please drive carefully and treat them like any other road construction crew. Be careful of spraying and pooling water.

Water service impacts

We will not turn your water off during flushing activities. In rare cases, you may see discolored water at your tap or experience lower pressure. Find more information in the Report discolored water or low pressure section below.

Notification before flushing

For our planned flushing work, we post signs in areas where we will be working.

Parking impacts

An orange and white no parking sign is perched on the curb onto the street. On the street is a spray painted P with a circle and a slash through it.

We need space to do our work and may temporarily restrict parking. If there is a no parking sign directly in front of your home or business, you may need to park in another place.

To do our flushing work, we need access to hydrants and small, circular valve covers in the street. We will use no parking signs a few days before our work to let you know where we need space. We try to clearly mark the locations we need to access; however, if your vehicle is blocking our access, we may need to tow your vehicle.

Pooling water and blocked storm drains

Two workers in bright safety vests use shovels and brooms to clear fallen leaves off the road to clear a stormdrain.

Water running down the street is normal during flushing activities. Sometimes water pools at street corners or at storm drains. Our flushing crews clear streets and storm drains to reduce water pooling. If pooling does happen, it is only temporary and lasts less than one hour. If a storm drain frequently pools during rain events, report the blocked storm drain online or call 503-823-1700.

Report discolored water or low pressure

In rare instances, while we are flushing you might notice discolored water, lower water pressure, or in extreme cases unexpected loss of water pressure. You can report these to the Water Quality Line.

Discolored water is not consistent with the quality of water we intend to serve. If you have discolored water, you may choose to drink bottled water or water from your emergency supplies.

If you have discolored water, you can avoid pulling that water into your whole house’s plumbing. Avoid using tap water or running your washing machine, dishwasher, or ice maker until flushing is complete.

To check if discoloration has cleared, run the water at one tap for two to three minutes to see if it clears. If it does not clear, wait an hour and try again. When the water runs clear, run the water at any taps where you had discolored water.

Questions about flushing or want to report discolored water or low pressure? You can report these to the Water Quality Line.