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Flushing of Water Lines

Public Works & Natural Resources Annual Flushing Program

We flush the lines to keep water quality at its highest level and to ensure that fire hydrants are operational. The benefits realized in water quality and fire protection far outweigh the comparatively small amount of water released during the flushing program.

Citizens may notice low water pressure, discolored water, or no water for short periods of time when flushing is taking place in their neighborhood. We recommend citizens limit water use, and particularly avoid using hot water when flushing is occurring in their immediate area.

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Utility Operations


2014 Flushing Schedule

Download a PDF version of the map and schedule to enlarge or print >

map of flushing by zone

April 21 - 25:

Crew A: Begins at Highway 66 south to 17th Avenue, Airport Road east to Main Street

Crew B: Begins at Highway 66 south to 17th Avenue, Main Street east to County Line Road 1

Crew C: Begins at 1st Avenue south to Pike Road, Sunset Street east to Martin Street

April 28 - May 2:

Crew A: Begins at 17th Avenue south to 9th Avenue, Airport Road east to Main Street

Crew B: Begins at 17th Avenue south to 9th Avenue, Main Street east to County Line Road 1

Crew C: Begins at 1st Avenue south to Plateau Road from S. Fordham Street to S. Sunset Street, and from Pike Road south to Plateau Road from S. Sunset Street east to Martin Street

May 5 - 9:

Crew A: Begins at 9th Avenue south to 1st Avenue, Airport Road east to Main Street

Crew B: Begins at 9th Avenue south to 1st Avenue, Main Street east to 1 mile east of County Line Road 1

Crew C: Begins at Rogers Road south to Plateau Road, N. 75th Street east to S. Fordham Street

We will make every attempt to stay on this schedule, but it is subject to change based on weather and unforeseen problems. If you have any questions, feel free to contact Utility Operations at 303-651-8468.


Frequently Asked Questions

Q. Why does the City of Longmont flush water mains?
A. Flushing helps maintain water quality. The water entering distribution mains is of very high quality; however, water can deteriorate in distribution mains if the mains are not properly managed and unidirectional flushing is a technique for managing a water distribution system.

Q. How does flushing improve water quality?
A. The City of Longmont water distribution system is a complex network of pipes and storage reservoirs where sediment or deposits may naturally accumulate over time. The flushing program removes sediment and ensures that the distribution system is operating correctly.

Q. Where does the water go?

A. The City of Longmont has a network of storm drainage pipes, ditches, and drainage basins that directs water to various detention ponds, creeks, ponds, and rivers. The water utilized during the flushing program also uses these pipelines and drainage ways. This allows water to get re-used in various ways, whether it goes to a local farmer through an irrigation ditch or into a river for re-use downstream. Local lakes like McIntosh Lake and Union Reservoir can be fed in some ways by these networks of pipes. Additionally, the City of Longmont accounts for this type of water usage through the Water Resources Division.

Q. How much water is used to flush mains?

A. The amount of water used to flush a particular section of pipe depends on a lot of factors, such as water main size and system pressure. A typical residential fire hydrant can flow on average between 1500 – 2000 gallons per minute. Flushing uses on average .005% (1/2 of 1%) of the drinking water that the City of Longmont uses on a yearly basis.

Q. How do I know when my area will be flushed?
A. Each year, an ad is placed in the Longmont Times-Call newspaper the Sunday before flushing begins. Information is also published in City Line, the monthly newsletter included with all City of Longmont utility bills, our Longmont social media accounts, and online to this web page. All sources indicate by map the date(s) that we will be flushing the water supply system that services your home. It’s always possible that these dates can change if we run into any unanticipated problems during the program. We strive to stick with our published schedule.

Q. When does flushing normally occur?
A. Normally, flushing takes place for approximately a 3 week period during early spring. Water crews flush the lines from 7:00 a.m. - 3:00 p.m.

Q. What should I do if I use water while my water line is being flushed?
A. If the cold water is clear, then the water is okay. If you encounter discolored water, shut the water off and wait several minutes. After waiting, check the clarity by running cold water for a few minutes allowing new water to work its way into your pipes. If not, wait a few more minutes and check again. This discoloration only affects the appearance of the water; it does not affect the taste or water quality.

Q. Why should I only use cold water when the crews are in my area?
A. The water system feeds both your cold and hot water system in a typical home. If you happen to use hot water during flushing, it may be necessary to drain your hot water tank. If this happens, stop using water immediately, and wait until crews are out of the area to continue hot water use.