Nitrate In Drinking Water In Hawaii
What residents of Hawaii need to know about nitrate in drinking water — including how it enters water, which utilities have documented violations, and what steps to take.
Source: EPA SDWIS, Hawaii Department of Health — Safe Drinking Water Branch (HDOH SDWB), CDC · Last reviewed: 2025-01-01
Quick Answer
Is nitrate in drinking water a real concern in Hawaii?
Yes — Hawaii has documented nitrate issues in some aquifers on Oahu and Maui linked to legacy sugarcane and pineapple agriculture and more recent residential development with septic systems.
Is this mostly a public-water issue, a private-well issue, or both?
Both public water systems drawing from affected aquifer zones and private well users in agricultural or high-septic-density areas on Oahu, Maui, and the Big Island.
What is the main reason residents should care?
Decades of sugarcane and pineapple cultivation in Hawaii — crops that required intensive fertilizer application — have left elevated nitrate in some aquifer zones. Residential development in former agricultural areas with septic systems adds to nitrate loading in affected areas.
Key Facts
| EPA Nitrate MCL | 10 mg/L as N |
| Agricultural legacy | Sugarcane and pineapple cultivation left elevated nitrate in some aquifer zones |
| Affected areas | Central Oahu, central Maui, and some Big Island agricultural areas |
| Residential addition | Septic systems in former agricultural areas add nitrate loading to affected aquifers |
| State oversight | Hawaii Department of Health — Safe Drinking Water Branch (HDOH SDWB) |
Why This Matters in Hawaii
Hawaii's volcanic geology creates unique groundwater flow pathways. Aquifers in volcanic rock can be recharged rapidly from the surface. Former sugarcane and pineapple plantation areas on Oahu (central Oahu), Maui (central Maui), and the Big Island carried decades of intensive fertilizer application. Some aquifer zones in these areas have documented elevated nitrate. Oahu's Pearl Harbor aquifer and central Oahu aquifer systems have been monitored for nitrate. Residential development in former agricultural areas adds septic system nitrogen loading. HDOH's Safe Drinking Water Branch monitors public water systems and provides guidance on private well testing.
Critical — Infants Under 6 Months
Do not use tap water that exceeds 10 mg/L nitrate-nitrogen to prepare infant formula or feed infants under six months. Boiling will concentrate nitrate — do not boil. Use bottled water or a certified reverse osmosis system (NSF/ANSI 58) until the issue is resolved.
Hawaii Utilities With Nitrate Violation Records
The utilities listed below have at least one nitrate violation on record in EPA's SDWIS database. Violations may be open or resolved — see individual utility pages for current status and risk level.
How Nitrate Gets Into Drinking Water
Agricultural fertilizer and manure runoff
Nitrogen-based fertilizers and animal waste applied to Hawaii cropland can leach into groundwater or run off into surface water supplies. This is the dominant nitrate pathway in most agricultural regions.
Septic system effluent
Failing or poorly sited septic systems release nitrogen-rich wastewater near drinking water wells. Rural areas with high well density and aging septic infrastructure face elevated risk.
Concentrated animal feeding operations (CAFOs)
Large livestock facilities generate significant waste. Lagoon leaks and overapplication of manure to nearby fields can create localized nitrate hotspots in groundwater.
Natural geological deposits
In some regions, naturally occurring nitrogen compounds in soil and bedrock contribute background nitrate levels to groundwater independent of agricultural activity.
Who Should Pay Closest Attention
Households with private wells in former agricultural areas on Oahu, Maui, and the Big Island should test for nitrate. Families with infants using private well water in these areas should confirm nitrate levels before using the water for formula preparation.
Households with infants under six months
Pregnant residents
Private well owners in agricultural areas
Households near livestock operations or CAFOs
Rural residents on shallow groundwater wells
Households with older or failing septic systems nearby
How to Check Your Situation in Hawaii
- 1
Identify your water utility. Use the ZIP lookup below or browse the Hawaii utility directory on this site.
- 2
Read your utility's page on this site to see its current risk level and any open nitrate violations.
- 3
Review your utility's most recent Consumer Confidence Report (CCR) — mailed annually or available on the utility's website. It must disclose any MCL exceedances.
- 4
If you are on a private well, arrange testing at a Hawaii Department of Health — Safe Drinking Water Branch (HDOH SDWB)-certified lab. Your state health department maintains a list of certified labs. Annual testing is recommended in agricultural areas.
- 5
If you have an infant under six months, use bottled water or a certified RO system (NSF/ANSI 58) immediately as a precautionary measure — do not wait for test results if you are in a high-risk area.
- 6
If your utility issues a nitrate exceedance notice, follow their guidance and do not use tap water for infants until the issue is resolved.
Treatment Options
Carbon filters and boiling do not remove nitrate. Only the options below are effective.
NSF/ANSI Standard 58 — Reverse Osmosis
RO systems certified to NSF/ANSI 58 reduce nitrate by 85–95% at the point of use. Under-sink installation required. The most practical residential option for nitrate concerns.
Distillation
Distillation units effectively remove nitrate along with most other dissolved contaminants. Suitable for drinking and cooking water — not whole-house use.
Anion Exchange
Ion exchange systems designed for nitrate removal exchange nitrate ions for chloride on a resin bed. Effective as a point-of-entry system; requires periodic regeneration and monitoring.
Carbon filters do NOT remove nitrate
Standard pitcher filters, faucet filters, and under-sink carbon units — including those certified NSF/ANSI 42 or 53 — do not remove nitrate. Do not use these for nitrate reduction.
Frequently Asked Questions
Related Pages
Nitrate — National Overview
All U.S. utilities with nitrate records
Hawaii State Overview
All utilities and water quality data
Lead in Drinking Water
A separate but common concern
Reverse Osmosis Guide
Removes 85–95% of nitrate
Well Water Guide
Private well testing and safety
All Contaminants
Complete reference library
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.