Tracing Atlanta's Drinking Water from Source to End User

Atlanta distributes between 70 and 115 million gallons of water per day, to more than 1.2 million end users spread across 379 square miles. All of this water is distributed through 2,790 miles of water mains that branch out throughout the city like arteries in the human body. Water mains, are large diameter underground pipes, ranging in size between 2" and 72" transferring water between the source and end user. After leaving the source, raw water is pumped to one of two water treatment plants or WTP's treating approximately 200 million gallons of raw water on a daily basis. Raw water treatment takes approximately 24 hours between input and output.   

Once treated, raw water is transmitted into the distribution system for transmission to end users all around Atlanta. Large water mains ranging in size between 48 and 72 inches in diameter, branch out from the WTP's supplying water to 12 water storage tanks located throughout the city and a reservoir. These tanks distribute treated water to the various neighborhoods through progressively smaller water mains with the smallest typically between two and sixteen inches in diameter. These smaller water mains generally run under streets, and provide water to the end users (i.e. homes, businesses, factories) through smaller metered service lines connecting the water mains to the end users. These service lines are typically manufactured from cast iron, copper, or plastic, depending upon the date of installation.  

The treated water flowing through these water mains originates from three main sources. The vast majority, or 70%, of raw water is drawn from Lake Lanier, fed from the Chattahoochee and Chestatee Rivers, and captured by the Buford Dam since 1956. The remaining 30% of raw water is drawn from Lake Allatoona and 20 other smaller reservoirs throughout the metro-Atlanta area.  Raw water from these three sources is then pumped through water mains arriving at one of two WTP's that treat the water through various processes of filtration. 

There are two WTP's treating raw water in Atlanta. The Hemphill WTP was constructed in 1893, treats 65% of raw water used by Atlanta through 17 filtering processes, and has a treatment capacity of approximately 137 million gallons per day. The Chattahoochee WTP was constructed in 1962, treats the remaining 35% of Atlanta's raw water through 13 filtering processes, with a treatment capacity of approximately 65 million gallons per day. It takes around 24 hours to treat water passing through the 2 WTP's and all water distributed through the Atlanta water system is treated by one of these two plants. 

Treated water leaving these two WTP's can be distributed directly to users or diverted to storage in a series of tanks or a reservoir. There are 12 storage tanks scattered throughout Atlanta - 9 above ground and three below ground - storing 37 million gallons of treated water. In addition to these 12 tanks, there is a new reservoir located on the westside of Atlanta storing treated water.  The Westside Park Reservoir was completed in August 2021 in an old rock quarry and holds 2.4 billion gallons of emergency treated water reserves. The treated water is these reserves guarantees that water will be available for residential and commercial purposes for at least 30 days in the event of emergencies.

Treated water is distributed to either end users or storage through water mains. Larger water mains are located closest to the WTP's or storage tanks and reservoir.   Sizes of water mains decrease in size the closer they approach the distribution points near the end users.  Service lines, varying in size as small as one-half inch  connect between water mains and meters measuring flows, and then onto end users, providing water for both residential and  commercial purposes.   So the next time you swim or boat upon Lakes Lanier or Allatoona, you may be floating upon the same water that you might be drinking within the next several weeks.