Preparation Begins for Water Treatment Upgrade

Mora McLaughlinMedia Release

Pittsburgh, PA – As part of the Pittsburgh Water and Sewer Authority’s (PWSA) Community Lead Response, crews are performing extended water main flushing across the service area to prepare the system for the addition of orthophosphate. Orthophosphate is a food-grade additive that has demonstrated to be highly effective at reducing corrosion from lead pipes.


Due to high lead levels found in some homes, PWSA conducted an extensive study to determine if the Authority should use different water treatment methods to limit corrosion from lead service lines and plumbing. The Authority currently uses soda ash and lime to control for corrosion.


At the end of a year-long study, orthophosphate was found to be more effective than soda ash and lime at reducing corrosion. The Pennsylvania Department of Environmental Protection (PA DEP) agreed with the study’s findings and approved PWSA’s corrosion control upgrade to orthophosphate. Water systems in large cities across the country use orthophosphate successfully to reduce the risk of lead in water.


PWSA is in the process of constructing new equipment required to add orthophosphate. In addition, the Authority is preparing for this treatment upgrade by flushing the water distribution system. The flushing effort will span several months and take place across the water service area.


Over the next several months, PWSA will systematically flush the water system by opening fire hydrants. Flushing clears potential sediment from water mains and prepares the pipes for the protective coating that orthophosphate creates. Flushing will take place during the day and night and may cause temporary brown water for some nearby customers. Read the FAQ below for what to expect during the flushing process as well as more information on orthophosphate.


For more information on PWSA’s Community Lead Response, go to



What is orthophosphate?


Orthophosphate is a food-grade additive that we will begin adding at our treatment plants to help reduce lead levels in water. When water with orthophosphate runs through the system, it will create a coating on the inside of lead service lines, creating a barrier between the lead pipes and the water. This is called “corrosion control”. PWSA currently uses soda ash and lime for corrosion control but has found that orthophosphate will work even better.


Is it safe in my drinking water?


The Environmental Protection Agency (EPA) and the PA DEP recognizes orthophosphate as an effective additive in water in reducing lead levels. It is also recognized as safe by the U.S. Food and Drug Administration.


PWSA conducted a year-long study of several different additives that are used to reduce lead levels in water. After finding that orthophosphate would be most effective for PWSA’s system, the research was reviewed extensively by the PA DEP before being approved as part of the treatment process. Orthophosphate is used for corrosion control in Boston, Washington, DC, Cleveland, and Philadelphia. It is also used by Pennsylvania American Water Company who serve some customers in the City of Pittsburgh.


Why is it important for the water system?


PWSA exceeded the action level for drinking water in June 2016. Since then, we have been working to aggressively replace lead service lines. However, replacing every lead service line will take years. In the immediate term, an effective solution to address high lead levels is to use the most effective corrosion control, which benefits our entire drinking water system.


Why does PWSA need to “flush” the water system before adding orthophosphate?


Before PWSA can begin to add orthophosphate-treated water into the system, it must flush the water distribution system. To do this, PWSA crews will be strategically traveling through the drinking water system opening hydrants to let the water flush out of the mains in the street. This will help the water with orthophosphate create the protective barrier necessary for corrosion control.


Crews will start with our largest water mains in the system and will work at night so not to disrupt customers. As they complete flushing on the largest water mains, they will move to the smaller water mains and hydrants that are located on most city streets. This work will take place during the daytime.


How will I know you are flushing the water system in my area?


PWSA will be notifying customers via robocall who are near our crews flushing hydrants. If you live near a large water main, you may not notice our crews working during the nighttime. During daytime work, you will see fire hydrants running and crews taking samples.


There is a chance you will see brown water after flushing is completed in your area. This water is not unsafe but is unpleasant to see. To flush brown water from your internal plumbing, run the cold taps in your building at the lowest possible point until the water appears clear. There may be some no-parking signs posted while crews perform flushing to allow for enough room for equipment around hydrants.