Public water system · HI0000326
ActiveDillingham Ranch
At a glance
Dillingham Ranch (PWSID HI0000326) is an active community water system in Honolulu County, Hawaii. It reports serving 100 people through 53 service connections. Its primary water source is groundwater, and EPA lists it as privately owned. EPA's records list one violation for this system; it is not health-based, and the most recent began in January 2007.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
100
Service connections
53
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Dillingham Ranch compare with other water systems in Honolulu County?
By EPA's size categories, Dillingham Ranch is a very small system (500 people or fewer). Honolulu County has 38 active public water systems. Its population served is well below the county average of 29,687 people per system, and accounts for less than 0.1% of the 1,128,119 people reported by systems filed under the county. Across Hawaii, the 136 active systems average 11,181 people each. Nationally, the average active community water system reports serving 6,703 people, so Dillingham Ranch is well below that figure.
What does “community water system” mean?
A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. Hawaii has 119 active community water systems, 88% of the state's 136 active systems. Groundwater means the system draws its water from wells or springs fed by underground aquifers. 112 Hawaii systems (82%) list groundwater as their primary source.
Who owns and regulates Dillingham Ranch?
EPA lists Dillingham Ranch as privately owned. The HI state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 16 of the 38 active systems in Honolulu County (42%) are also privately owned.
Does Dillingham Ranch have drinking water violations?
EPA's records list one violation for this system; it is not health-based, and the most recent began in January 2007. By type: 1 monitoring and reporting. The contaminant or rule involved is Lead and Copper Rule. EPA lists 1 as resolved. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2007-01-01 | Monitoring and reportingFollow-up Or Routine LCR Tap M/R · code 52 | Lead and Copper Rulecode 5000 | No | Resolved |
The one violation in EPA's records.Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.
Dillingham Ranch: frequently asked questions
Who runs Dillingham Ranch?
Dillingham Ranch (PWSID HI0000326) is a community water system privately owned. It is regulated by the HI state drinking water program.
How many people does Dillingham Ranch serve?
Dillingham Ranch reports serving 100 people through 53 service connections in Honolulu County, Hawaii.
Where does Dillingham Ranch get its water?
EPA SDWIS lists this system's primary water source as groundwater. Groundwater means the system draws its water from wells or springs fed by underground aquifers.
Does Dillingham Ranch have any drinking water violations?
EPA's records list one violation for this system; it is not health-based, and the most recent began in January 2007. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.
Is Dillingham Ranch's water safe to drink?
AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. EPA's records list one violation for this system; it is not health-based, and the most recent began in January 2007. For current results, consult the system's annual water quality report, EPA ECHO, or the HI state drinking water program.
Where can I find Dillingham Ranch's water quality report?
As a community water system, Dillingham Ranch must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.
Other water systems in Honolulu County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Hnl-Windward-Pearl Harbor | Honolulu | 631,389 | Community | Groundwater |
| Waipahu-Ewa-Waianae | Honolulu | 217,479 | Community | Groundwater |
| Joint Base Pearl Harbor-Hickam | Honolulu | 65,230 | Community | Groundwater |
| Mililani | Honolulu | 50,573 | Community | Groundwater |
| Schofield Barracks | Honolulu | 37,920 | Community | Groundwater |
| Wahiawa | Honolulu | 23,348 | Community | Groundwater |
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About this data
Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.
Cite as: AquaCensus, “Dillingham Ranch, PWSID HI0000326, Hawaii”, https://aquacensus.com/water-systems/hawaii/dillingham-ranch-hi0000326 (data as of October 1, 2026).