Portland’s tap water meets or exceeds all federal and state safety standards for drinking water, positioning it as a high-quality municipal supply. The water is sourced primarily from a protected watershed, which contributes to its naturally soft and clean characteristics. Despite this high baseline quality, the safety of the water at the tap is influenced by two major factors outside the public distribution system’s control: the age and material of plumbing inside private homes, and the city’s ongoing, state-mandated project to construct a full filtration plant.
Portland’s Protected Water Source
The primary source for Portland’s drinking water is the Bull Run Watershed, a 102-square-mile protected area nestled in the Mount Hood National Forest. Restricted access and management by the Portland Water Bureau and the U.S. Forest Service ensure a high level of raw water purity. The watershed is primarily fed by high annual rainfall, averaging around 130 to 135 inches, which flows into the Bull Run River and two large reservoirs.
The two reservoirs store nearly 10 billion gallons of water, providing a reliable supply throughout the drier summer months. Because the source water is naturally high in quality, Portland has historically been one of the largest cities in the United States to operate without a full filtration system. This protected status helps minimize contaminants that typically require extensive treatment in other municipal water systems.
Regulatory Oversight and Testing Standards
The Portland Water Bureau (PWB) operates under the regulations of the U.S. Environmental Protection Agency (EPA) and the Oregon Health Authority, adhering to the requirements of the Safe Drinking Water Act. This regulatory framework requires continuous monitoring and testing to ensure the water is safe as it travels through the distribution system. The PWB conducts extensive testing, collecting approximately 4,700 water samples each year from over 270 locations.
These samples undergo nearly 50,000 annual tests for more than 200 regulated and unregulated contaminants, including industrial chemicals, heavy metals, and microorganisms. Current treatment processes focus on disinfection and corrosion control before the water reaches homes. The PWB adds chloramine, a combination of chlorine and ammonia, to ensure the water remains disinfected throughout the pipe network.
Sodium hydroxide and sodium carbonate are introduced to the water to modify its chemistry, a process called corrosion control treatment. This treatment makes the water less corrosive, preventing metals like lead from leaching out of older plumbing materials. This chemical adjustment is standard practice to comply with federal regulations and protect public health.
Localized Concerns from Home Plumbing
While the water leaving the public system is consistently safe, the most common source of potential contamination occurs within the property lines of individual homes and buildings. The PWB confirms that public water mains and service lines are lead-free, as Portland never used lead service lines and removed all known lead service connectors by 1998. The lead risk arises from older household plumbing materials, such as lead solder used to join copper pipes before 1985.
Lead can also leach into the water from brass faucets, fittings, and fixtures installed before 2014, when federal law tightened the definition of “lead-free.” When water stands motionless in pipes for several hours, it has more time to corrode these materials and absorb trace amounts of metal. The PWB’s corrosion control effort helps reduce this risk by creating a protective mineral coating inside pipes, significantly lowering measured lead levels.
Consumers can take steps to minimize lead exposure from household plumbing:
- Run the tap for 30 seconds to one minute, or until the water feels noticeably colder, to flush out standing water.
- Use only cold, fresh water for drinking, cooking, and preparing baby formula, as lead dissolves more easily in hot water.
- The Portland Water Bureau offers free lead-in-water testing to customers.
The Ongoing Filtration Project
The Bull Run Watershed is currently operating under a compliance agreement with the Oregon Health Authority (OHA) to construct a full filtration facility. This project was mandated following low-level detections of the microscopic parasite Cryptosporidium in the source water. Cryptosporidium is a protozoan that can cause gastrointestinal illness, and it is highly resistant to chloramine disinfection.
The filtration plant is designed to eliminate this disease-causing organism, along with other particles and debris. The OHA has set a compliance deadline for the new facility, requiring the water to meet all surface water and Cryptosporidium treatment requirements by September 30, 2027. While the facility is under construction, the PWB continues with interim measures, including intensive watershed protection and monitoring.
The new facility is an immense infrastructure undertaking, with cost estimates recently exceeding $2.13 billion. Once operational, the filtration process will physically remove Cryptosporidium oocysts and other contaminants, providing a more reliable barrier against waterborne pathogens and turbidity events. This change is a significant shift for the city, moving its primary water source from an unfiltered system to a fully treated one to ensure long-term public health protection and regulatory compliance.