Cleaning the Water Distribution Systems

Beginning last week on March 25, 2024,  Fairfax Water and Loudoun Water  began flushing their water distribution systems. Because Prince William Service Authority purchases most of their water from Fairfax Water, they too, have embarked on the spring flushing of the water distribution system. The Washington Aqueduct which supplies water to D.C. and Arlington and a small area of Fairfax also began their annual program at the same time this year. Each spring for about 12 weeks in Washington DC,  Arlington , Fairfax Water and Loudoun Water flush their water mains by opening fire hydrants and allowing them to flow freely for a short period of time. In addition, the Washington Aqueduct, Fairfax Water and Loudoun Water temporary change how the water is disinfected.

For most of the year, chloramines, also known as combined chlorine, is added to the water as the primary disinfectant. During the spring the Washington Aqueduct and Fairfax water treatment plants switch back to chlorine in an uncombined state, commonly referred to as free chlorine. This free chlorine reacts with sediments suspended during flushing and kills bacteria that may be in the bio-film that forms on the pipe walls. Many water chemistry experts believe this short exposure to a different type of disinfectant maintains a low microbial growth in the bio-film and improves the quality and safety of the water. This change will last through May 6th 2024 for Fairfax Water,  Loudoun Water, Prince William Service Authority, and the Washington Aqueduct.

This change in disinfection is an annual program to clean the water distribution pipes and maintain high water quality throughout the year. The U.S. Army Corps of Engineers Washington Aqueduct provides water to the District of Columbia, Arlington County, and Falls Church and McLean VA. Fairfax Water provides water to the Fairfax county (purchasing it from the Aqueduct for Falls Church and McLean) and parts of both Loudoun and Prince William County. Both Fairfax Water and the Aqueduct switch from chloramine to chlorine during this period. DC Water is completing their pipe flushing. Washington Suburban Sanitary Commission (WSSC) abolished its preventative flushing program years ago to save money. In recent years WSSC has been plagued with discolored water complaints and will flush a hydrant on request.

Those of you in the Fairfax, Loudoun,  Arlington and Washington DC service areas may notice a slight chlorine taste and smell in your drinking water during this time, this is not harmful and the water remains safe to drink. If you are a coffee and tea lover like me, use filtered water or leave an open container of water in the refrigerator for a couple of hours to allow the smell to dissipate. Water customers who normally take special precautions to remove chloramine from tap water, such as dialysis centers, medical facilities and aquarium owners, should continue to take the same precautions during the temporary switch to chlorine. Most methods for removing chloramine from tap water are effective in removing chlorine. The annual chlorination is important step to remove residue from the water distribution system.

Flushing the water system entails sending a rapid flow of chlorinated water through the water mains. As part of the flushing program, fire hydrants are checked and operated in a coordinated pattern to help ensure their operation and adequate flushing of the system. Water pressure should not be significantly impacted during this process. The flushing removes sediments made up of minerals which have accumulated over time in the pipes as well as bacteria on the bio-film. An annual flushing program helps to keep fresh and clear water throughout the distribution system. Removing the residue ensures that when the water arrives in your home, it is the same high quality as when it left the water treatment plant.

During the spring flushing program your water may look or taste different. Free chlorine is quicker acting than chloramines, which allows it to react with sediments suspended during the flushing which may result in temporary discoloration and the presence of sediment in your water. These conditions should be of very short duration and the water is reported to be safe. Though, remember you still need to treat tap water before using it in a fish aquarium. Disinfectants can harm fish. Check with a local pet store to learn what types of chemicals you need to add to the tank to neutralize the effects of the disinfectant.

During the spring flushing you may notice a white of bubbly appearance or a chlorine taste and odor in your drinking water. The bubbly appearance is simply a result of the oxygen in the water being stirred up during flushing causing visible air bubbles. Let the water sit for a few seconds and you will see the bubbles clear from bottom to top. The chlorine taste can be removed by filter or by simply letting the water sit in an open container in your refrigerator. If you are especially sensitive to the taste and odor of chlorine, filters commonly used in refrigerators are very effective at removing chlorine- change your filter.