Water Quality & Treatment
Everyone expects to turn on their tap and have clean, safe drinking water flow out. But this takes committed water professionals who work together to fulfill the City’s needs 24 hours a day, seven days a week, 365 days a year. And they do it in full compliance with all local, state, and federal regulatory requirements--that’s how you know your water is healthy, safe, and pure.
Curious about how your water is made safe and healthy? Take a look at our annual Water Quality Report (pdf) to see all the details.
The Water Quality Report is compiled every year to share with Durham residents the many ways we manage the City’s water. We move raw water from the lakes to the treatment plants. We test and analyze to ensure what flows from your tap is fresh and healthy. And we improve the facilities and equipment to meet growing need and make the system better.
- Main Water Sources
- Water Treatment Facilities
- Water Treatment Process
- Chemicals Added
- Water Storage
- Pipes and Flushing
- Water Meters
- Testing for Lead
- Drinking Water
Durham has two main sources of raw water. These are Lake Michie, which was completed in 1926, and Little River Reservoir, which was completed in 1987. Lake water is delivered to the City’s treatment plants using a combination of gravity flow and electric and hydro-powered pumping. This keeps electricity costs as low as possible.
The staff of the Water Supply and Treatment Division are in charge of the Lake Michie and Little River pumping stations. They also operate the City’s two water treatment facilities.
The pumps at Lake Michie and Little River send raw, untreated water to Durham’s two water treatment plants, where it’s stored in reservoirs. The reservoir at Brown Water Treatment Plant (pictured) holds approximately 90 million gallons and the reservoir at Williams Water Treatment Plant holds about 45 million gallons.
- Williams was completed in 1917.
- Brown was completed in 1979.
- They have a combined capacity of 64 million gallons of water a day.
- Durham residents and businesses use an average of 27 million gallons a day.
Together, those reservoirs store two or three days’ worth of water for the City of Durham. That's why we can handle a line break, routine maintenance, or unexpected disruption and still provide continuous service.
The raw water from the reservoirs flows into clarifier tanks, where clouds of floating particles are removed through processes called coagulation, flocculation, and sedimentation.
- Coagulation happens when positively-charged chemical coagulants attract particles of sediment and organic matter.
- These particles then clump together and form flocs, through a process known as flocculation.
- Sedimentation occurs when these flocs of particles settle to the bottom of the clarifier tank, where rake-like equipment scoops them out.
Filtration comes next. Clear, sediment-free water leaves the clarifier to flow through filters made of crushed anthracite coal, sand, and gravel. This removes any tiny particles the earlier processes missed.
You can learn more about the water treatment process to find out how our water professionals do this important work.
Several chemicals are added to the water as it’s treated. The concentrations of each of the majority of these chemicals must meet EPA standards.
- Chloramines for disinfection
- Orthophosphate to prevent pipe corrosion
- Sodium hydroxide for pH balance
- Fluoride to promote dental health.
Once treated and disinfected, drinking water is stored in covered tanks called clear wells. The City stores several millions of gallons of treated water in clear wells on the treatment plant sites ready for distribution. Treated water is also stored in elevated and ground level water storage tanks located throughout Durham. Levels in the towers are monitored remotely and usually filled each evening using off-peak pumping strategies. Towers and elevated tanks help maintain pressure in the distribution system so that each household and business has sufficient flow.
- Water Supply and Treatment personnel respond to questions and complaints about water quality.
- They analyze and adjust the treatment process each day as needed.
- They spend time collecting and analyzing samples to monitor water quality across the system.
The distribution system delivers water from the treatment facilities through 1,400 miles of water lines to approximately 95,000 connections in Durham. These homes, businesses, and institutional customers rely on staff to maintain both the quality of the water and the integrity of the lines, pipes, and other infrastructure. Flushing is one mechanism used to move water quickly through the lines for a number of reasons.
In areas where there are dead-end pipes or areas of low water use, small particles can settle in the pipes. Over time, these deposits might cause color, odor, or taste issues. They can also become stirred up if there’s a water line break. This is why, when crews respond to a break and complete the repairs, hydrants in the area are often flushed to clear the water flowing into customers’ taps.
Periodically, our employees conduct planned flushing to address these issues.
- See the Flushing FAQs (PDF) to learn more about this practice.
Flushing is also recommended for businesses, schools, or facilities after an extended closure, as water left standing in the pipes can become stagnant and present certain health risks.
- See our Flushing Water Systems FAQs (PDF) for guidelines.
The Meter Maintenance work group conducts meter reading and provides routine and emergency response to water meter problems including leaks, unusual consumption rates, and water pressure concerns.
One major undertaking of the Meter Maintenance work group is oversight of the Automated Meter Reading (AMR) project. The benefits of an automated meter reading system include convenience for both the City and the customer. With AMR, the meter readers can collect meter readings much quicker and more safely by simply driving past meter locations.
The electronic meters will assist customers in detecting leaks and will assist utility staff in detecting malfunctioning or tampered meters. Additionally, this timely information, coupled with analysis, can help both utility staff and customers better manage the City’s potable water usage.
The City of Durham is required to test for lead and copper every three years.
Our most recent results come from tests conducted in 2022. The analysis found no detectable lead in the drinking water leaving our treatment facilities. During a testing year, samples are collected and analyzed after standing unused in the plumbing of a number of volunteer homes for at least six hours --usually overnight.
We’re happy to announce our water wins taste tests!
Panelists at the 2019 Annual Conference of the N.C. Water Works Association - Water Environment Association sampled tap water from across the state. They declared water from our Williams Water Treatment Plant the best in North Carolina!
It was the second year in a row we received that honor and we’re quite pleased. We couldn’t agree more!