Honolulu – Hawaii – Water Quality Report 2025: PFAS Testing, Infrastructure Concerns & Safety across your city
The Honolulu Board of Water Supply (BWS) manages a comprehensive water system serving approximately 1 million residents across the island of Oahu. Established in 1929 as a semi-autonomous agency, the BWS operates an extensive network of wells, pumping stations, reservoirs, and water treatment facilities, delivering roughly 145 million gallons of water daily to Hawaii’s most populous island.
Honolulu derives almost all of its drinking water from groundwater sources, with the majority coming from underground aquifers that are naturally filtered through the island’s volcanic rock formations. The system includes over 2,100 miles of pipelines and more than 170 potable water sources, primarily deep wells that tap into Oahu’s extensive basal aquifer system. The BWS has implemented significant sustainability measures to protect this precious resource, focusing on watershed protection, advanced water treatment, and conservation initiatives. The utility meets or exceeds all federal and state drinking water standards, providing safe, dependable water service while addressing challenges including infrastructure maintenance, saltwater intrusion prevention, and emerging contaminant monitoring.
Honolulu Water Quality: Current Status (2024-2025)
Latest Testing Results
- Comprehensive Monitoring: The BWS conducts over 100,000 water quality tests annually across its network, ensuring consistent monitoring from source to tap throughout Oahu’s water distribution system.
- Compliance Status: Honolulu’s drinking water fully meets all federal EPA standards and Hawaii Department of Health regulations, with test results published in annual Consumer Confidence Reports available to all residents.
- PFAS Monitoring: Recent testing has detected low levels of per- and polyfluoroalkyl substances (PFAS) in several well systems, though all detections remain below current EPA health advisory levels, with continued monitoring in place.
Island Water Sources
- Groundwater Dependence: Nearly 100% of Honolulu’s drinking water comes from groundwater sources, primarily from the basal aquifer system that naturally forms within Oahu’s volcanic rock formations.
- Aquifer Protection: The BWS maintains rigorous protection of watershed areas and recharge zones that feed the island’s aquifers, including partnerships with conservation organizations to preserve forested upper watersheds.
- System Redundancy: Strategic distribution of wells across the island provides system resilience, though challenges emerged in 2021-2022 when three wells had to be temporarily shut down due to concerns about potential contamination from the Red Hill fuel facility.
Treatment Processes
- Minimal Treatment Required: Honolulu’s naturally filtered groundwater typically requires less intensive treatment than surface water sources, with the majority of water sources receiving chlorination disinfection and pH adjustment.
- Specialized Facilities: For areas with specific contaminant concerns, the BWS employs advanced treatment technologies including granulated activated carbon filtration systems in Central Oahu and North Shore areas to remove agricultural chemicals.
- Quality Control: Continuous electronic monitoring throughout the system provides real-time data on water quality parameters, allowing for immediate response to any detected issues.
Infrastructure Management
- Pipeline Renewal: The BWS has accelerated its water main replacement program, addressing aging infrastructure with a focus on areas with history of breaks or leaks, replacing approximately 6-10 miles of pipeline annually.
- Water Loss Prevention: Implementation of advanced technologies including acoustic leak detection systems and smart meters helps identify and address water losses throughout the distribution system.
- Reservoir Maintenance: Regular inspection and maintenance of the system’s 170+ reservoirs ensures water storage quality and structural integrity for reliable service even during emergency situations.
Sustainability Initiatives
Honolulu’s Board of Water Supply has implemented a comprehensive sustainability program that balances current needs with long-term resource protection. The Water Master Plan guides infrastructure investments while the Water Conservation Plan promotes efficiency through consumer education, rebate programs for water-efficient fixtures, and xeriscaping incentives. The BWS’s watershed protection efforts include partnerships with conservation organizations to maintain healthy forests that capture rainfall and recharge aquifers. Climate change adaptation strategies address sea level rise concerns that could affect coastal wells through saltwater intrusion. The utility also invests in renewable energy at pumping facilities and has developed water recycling capabilities at the Honouliuli Water Recycling Facility, providing non-potable water for irrigation and industrial use to reduce demands on drinking water supplies.
Recommendations for Honolulu Residents
Test Your Water
Request water quality testing by calling 808-748-5041 or visiting boardofwatersupply.com. Testing is particularly recommended for older homes or those with aging plumbing systems that may contribute to water quality concerns.
Practice Water Conservation
Participate in the BWS conservation programs, including rebates for WaterSense fixtures and xeriscaping projects. Call (808) 748-5041 or visit boardofwatersupply.com/conservation to apply for available incentives and learn water-saving techniques.
Consider Home Filtration
While Honolulu’s water meets all safety standards, homes with copper pipes manufactured before 2014 may benefit from NSF-certified filters (Standard 53) if concerned about potential lead from solder or fixtures.
Follow Conservation Guidelines
Be aware of voluntary and mandatory conservation notices during dry periods. When in effect, reduce outdoor irrigation, avoid washing vehicles at home, and fix leaks promptly. Check boardofwatersupply.com for current conservation status updates.
Report Issues
Contact 808-748-5000 immediately for water main breaks, water quality concerns, or unexplained increases in water usage. For after-hours emergencies, call the same number, which is monitored 24/7 by BWS personnel.
Quality News About Your Water
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Frequently Asked Questions
Is Honolulu’s tap water safe to drink?
Yes, Honolulu’s tap water meets all federal and state drinking water standards and is safe to drink. The Board of Water Supply conducts over 100,000 tests annually to ensure water quality and safety throughout the system.
Honolulu’s drinking water comes primarily from groundwater sources naturally filtered through volcanic rock. This natural filtration process often results in high-quality water requiring minimal treatment. The BWS adds chlorine for disinfection and makes pH adjustments at some facilities to reduce pipeline corrosion, but otherwise, the water receives minimal processing before delivery to homes.
Why does my water sometimes taste salty?
Slightly elevated salt levels can occur in some areas of Honolulu, particularly during periods of high water demand or drought when wells may be pumped more intensively. This can cause what’s known as “upconing” where deeper saltwater is drawn up toward freshwater zones.
To address this concern:
1. The BWS carefully monitors chloride (salt) levels in all water sources
2. Wells showing elevated salinity are rested or pumped at reduced rates
3. Water from different sources is blended when necessary to maintain quality
If you notice persistent salty taste in your water, contact BWS at 808-748-5041 so they can investigate the specific situation in your area.
How does Honolulu protect its water supply?
Honolulu employs a comprehensive approach to protecting its precious water resources:
• Watershed protection: Partnerships with conservation organizations to maintain healthy forest ecosystems that capture rainfall and recharge aquifers
• Monitoring and testing: Extensive water quality testing program with over 100,000 tests conducted annually to ensure water safety
• Sustainable pumping: Careful management of pumping rates to prevent saltwater intrusion and maintain aquifer health
• Source water assessments: Regular evaluation of potential contamination sources near wells and implementation of protection measures
• Public education: Programs to promote water conservation and proper disposal of potential contaminants
These combined efforts help ensure the long-term sustainability of Oahu’s groundwater resources for future generations.
Are there water restrictions in Honolulu?
Honolulu occasionally implements water conservation measures depending on supply conditions:
Current Status:
• BWS requests voluntary conservation in some areas, particularly during summer months when demand increases
• Special attention is given to the Metro Honolulu and Aiea-Halawa areas where well closures related to Red Hill have reduced available supply
During Drought Conditions:
• BWS may issue mandatory conservation notices requiring specific actions
• Restrictions typically focus on reducing outdoor water use, such as limiting landscape irrigation to specific days or times
• Prohibition on wasteful practices like allowing water to run off properties
For current conservation status and any active restrictions, visit boardofwatersupply.com or call 808-748-5041.
Contaminants of Concern
PFAS (Per- and Polyfluoroalkyl Substances)
Source: Industrial and consumer products, firefighting foam, and other sources; detected at low levels in some Oahu groundwater sources in recent testing
Health Effects: Potential impacts on immune system, thyroid function, and other health concerns with long-term exposure to elevated levels
Current Levels: Low levels detected in some wells, all below current health advisory levels EPA Action: New health-based standards being developed; BWS monitoring closely
Salinity (Chlorides)
Source: Natural seawater intrusion into groundwater, especially during periods of intensive pumping or drought; Honolulu’s island location makes this a constant management concern
Effects: Primarily aesthetic (taste) concerns at current levels; very high levels can cause corrosion of plumbing fixtures and appliances
Management Approach: Careful monitoring of chloride levels in wells, strategic pumping to prevent upconing, blending of water sources when necessary, and development of deeper monitoring wells to track saltwater intrusion
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