The tap water supplied to Portland, Maine, is consistently regarded as safe to drink and of very high quality. The water system operated by the Portland Water District (PWD) routinely meets or surpasses all mandated state and federal drinking water standards set by the Safe Drinking Water Act (SDWA). This high standard of purity is maintained through a combination of a naturally protected source, comprehensive watershed management, and advanced treatment processes. The public water supply in the Greater Portland area is considered one of the best in the nation.
The Protected Source and Management Authority
The primary water source for the Greater Portland area is Sebago Lake, which is one of Maine’s deepest and second-largest lakes. The exceptional natural quality of this water body is maintained by a vast and actively protected 450-square-mile watershed. This extensive protection effort minimizes human activity and potential pollutants from entering the supply, which is the first line of defense for water quality.
The Portland Water District is the agency responsible for managing the water supply, treatment, and distribution for nearly one-sixth of Maine’s population. The district’s dedication to source protection is so effective that the lake is one of only about 50 surface water supplies in the country exempt from federal filtration requirements. PWD continuously monitors the lake’s water quality, including the 11 major streams that flow into it, showing stable, excellent quality since the 1970s.
Treatment Processes and Regulatory Compliance
Although the source water is naturally pure, the Portland Water District employs a multi-step treatment process before distribution. The process includes initial screening, followed by powerful disinfection using ozone, a technology that was a pioneering effort for a free-standing plant in New England. Ozonation is highly effective at inactivating pathogens like Giardia and viruses.
Further disinfection is provided by ultraviolet (UV) light treatment, which targets resistant microorganisms such as Cryptosporidium. The final treatment step involves adding chloramines, a chlorine derivative, which maintains a protective disinfectant residual as the water travels through the distribution network. PWD’s certified laboratory analyzes nearly 6,000 samples and performs 16,000 analyses annually, consistently demonstrating full compliance with all regulations required by the Safe Drinking Water Act.
Corrosion control is also integrated into the treatment process to protect the public infrastructure and household plumbing. The naturally slightly acidic pH of the Sebago Lake water, typically around 6.7, is adjusted to a less corrosive level of approximately 8.0 using sodium hydroxide. This alkalinity adjustment creates a protective coating on pipe interiors, minimizing the potential for metals to leach from pipes and fixtures into the drinking water.
Current Status of Key Contaminants
The Portland Water District recently completed an inventory of its infrastructure, confirming no lead mains or service lines exist within the public water system. This finding, which involved reviewing over 56,000 service records and conducting physical inspections, is a significant public health achievement. The district’s proactive corrosion control program further reduces the low risk of lead exposure from older household plumbing materials.
Regarding emerging contaminants, specifically per- and polyfluoroalkyl substances (PFAS), the Portland water supply has demonstrated no measurable levels. Recent testing conducted in March 2024 found no detectable amount of PFAS, meeting both the new federal standards and Maine’s state regulations. The water system also maintains consistent compliance with microbiological standards; total coliform bacteria tests are performed five days a week, and detection is extremely rare. Testing for disinfection byproducts (DBPs), which can form during the chlorination process, shows levels far below the established health-based limits.
Addressing Water Quality in Private Plumbing
While the PWD ensures the water is safe up to the property line, the quality at the tap can be affected by internal plumbing. The water district is responsible for the water main and the service line up to the curb stop or property line. However, the homeowner is responsible for the service line portion entering the building, internal pipes, and fixtures. Issues like corrosion or lead leaching within the home are therefore the homeowner’s responsibility to address.
In older homes, lead can still be present in brass fixtures, solder connecting copper pipes, or the private service line portion. Residents can take simple actions to reduce potential exposure, such as flushing the tap for 30 seconds to several minutes after the water has been sitting unused for a period of hours. For those with ongoing concerns, point-of-use filters, such as pitcher filters or faucet-mounted systems certified to remove lead, can provide an additional safeguard.