Understanding Phoenix's Water Quality
The city of Phoenix provides drinking water to more than 1.5 million people within our 540 square-mile service area. On average, about 95 percent of Phoenix's water comes from surface water (lakes and rivers) and the remaining water comes from groundwater (wells). Each May, the city distributes and posts to the web a Water Quality Report that contains important information about the quality of your water. Phoenix is committed to providing the highest quality drinking water and service to our customers.
Testing the Water to Ensure Only the Highest Quality
More than five million tests and measurements are conducted each year to ensure high quality tap water in Phoenix. It is tested for more than 100 substances, and is monitored throughout the year to ensure that it meets the rigorous standards set forth by the U.S. Environmental Protection Agency (EPA), the Arizona Department of Environmental Quality, and the Maricopa County Environmental Services Department.
From time to time various groups develop desired standards for drinking water that differ from those established by the EPA. While these theoretical standards may start with good intentions, comparing Phoenix’s test results, which are in full compliance with EPA standards, to artificial standards can create confusing, incomplete, and many times extremely misleading information that is unfair to our customers and the city. Be assured that Phoenix complies with current EPA requirements, works with water associations to remain up to date on water quality standards and is committed to protecting public health and safety.
Water Treatment Process Provides Superior Drinking Water
Testing on tap water begins before it enters the water treatment plant. Plant staff works closely with laboratory technicians to determine the composition of the raw water that enters the plant so the treatment process can be fine tuned to ensure that the water is treated effectively to the highest standards. The water is monitored manually and electronically throughout the process to determine if adjustments to treatment must be made. The system used by the city of Phoenix to treat surface water is a highly effective multi-step process, which can be seen in the illustration and explanation below:
Basic Water Treatment Process
Screening and Presedimentation -Large particles such as plant matter debris, and other materials commonly found in river water are removed by screens or settle to the bottom of the presedimentation tank.
Coagulation, Flocculation and Sedimentation - A chemical coagulant, such as alum or ferric chloride, is added to the water. This causes the tiny particles to cling together and become heavy enough to settle to the bottom of the basin.
Filtration - The cleaner water on the top then passes through filters to remove remaining particulate matter.
Disinfection -A small quantity of chlorine, a disinfectant, is added to prevent microbial growth. Also a small quantity of fluoride is added to prevent tooth decay.
Sampling and Testing the Water After It Leaves the Plant
After the water leaves the water treatment plant it enters the Phoenix water distribution system, which is comprised of about 7,000 miles of water mains, 70 reservoirs, 110 booster pump stations, 50,000 fire hydrants and 119,000 valves. At numerous points within the system, water quality inspectors take samples of the water, which are then analyzed at the lab to make sure your water continues to meet the highest standards along the many miles it travels to reach your tap.
Maintaining Our Distribution System to Ensure Continued Water Quality and Reliability
As part of the process of maintaining the high quality water and the integrity of the water distribution system, staff will flush the system in strategic locations so that the water quality is maintained. Crews from our Water Distribution Division also work hard to make sure that leaks in our water system never impact the delivery to your tap. And while there are times that water outages do occur due to aging lines or accidents, we do our best to keep customers informed and outage times short.
Aesthetics of Water Quality
Taste and Odor
Taste and odor are not regulated under drinking water health standards. However, these are harmless, aesthetic aspects that some consumers may notice. Algae that grow in the Valleywide canal system during the late summer and fall are a major source of a “musty” odor and taste detected by some consumers. Even though the algae are removed from the water during the treatment process, the odor may linger. The result is similar to removing a bouquet of fresh flowers from a room. Even though the flowers are gone, the aroma remains. The city of Phoenix is working to eliminate the aesthetic effects of algae through various programs, including a cooperative effort to remove algae from the SRP canals that feed the water treatment plants, and the use of activated carbon to absorb residual odors. You also can also reduce taste and odor in tap water by simply chilling the water in the refrigerator prior to consumption. Another easy method is to add a slice of lemon to the water.
Water hardness is measured by the presence of minerals, such as calcium and magnesium in tap water. These minerals originate from the soils our source water comes into contact with as it travels from and through watersheds to Phoenix’s water treatment plants. These minerals are leached into the water. Hard water can cause some types of scaling in pipes and water heaters, and on plumbing fixtures such as faucets and showerheads. Many people choose to install water softening devices that reduce the hardness in water. While the city cannot make recommendations as to the type or brand of device, we do suggest that those interested in purchasing a water softening system should contact the Arizona Water Quality Association at 480-947-9850.
If you already have a water softening system, and it needs to be set based on the "Total Hardness" level [usually indicated by Grains per Gallon or Parts Per Million (ppm)]. The settings for Phoenix tap water are listed below. Due to the size of the Phoenix water system and variations in source water throughout the year, the hardness numbers are reported as a range. So when setting your water softening equipment, it is suggested that the initial setting should be in the middle of that range, then adjust the setting to your preference as needed.
Total Hardness (Range)
|Parts per Million|
|11 - 17||190-289|
Learn more about the quality of your water?
EPA regulations require the Phoenix Water Services Department to publish a Consumer Confidence Report, which is also known as a Water Quality Report. The report is distributed each May and encompasses important information about Phoenix water for the previous year. Review the most current water quality report.