Is Hilo, HI Tap Water Safe to Drink?
Yes, Hilo tap water is safe to drink. Hardness is low at 30 PPM, and no contaminants exceed health guidelines. Most homes here don't need treatment.
Hardness Scale: Where Hilo Falls
0Slightly
60Moderate
120Hard
180Very Hard
250Extreme
400+
How Hilo Compares
Hilo's water is 78% softer than the national average of 138 PPM - ranking in the bottom 83% for hardness nationwide. Most homes here do not need a softener. Within Hawaii, it ranks #5 of 7 cities (43% below the state average of 53 PPM). Among smaller cities, Hilo ranks #214 of 288 for hardness.
What Hilo's Water Means for Your Home
Hardness: 30 PPM - Low Concern
Hilo's water is slightly hard at 30 PPM. Most households won't notice any issues at this level. Scale buildup is minimal, and a water softener would be overkill. Hilo is softer than 83% of US cities. If you're thinking about water treatment, contaminant filtration is where to focus your money, not softening.
Contaminants & Safety
Lead levels deserve attention. At 9.4 ppb, Hilo is above the ideal of zero, though below the EPA action level of 15 ppb (dropping to 10 ppb in November 2027 under the Lead and Copper Rule Improvements). The lead typically comes from aging service lines or interior plumbing, not the treatment plant. A point-of-use filter certified for lead at the kitchen faucet is a practical safeguard, especially in older homes.
What's in the Treatment Process
Chromium-6 is naturally present in Hilo's aquifer geology at 1.02 ppb — 51x the EWG health guideline. There's no federal legal limit for chromium-6 specifically (only total chromium), which is why EWG tracks it separately. All measurements are within federal legal limits. The EWG guidelines represent a more conservative, health-based standard.
| Contaminant | Detected | Health Guideline | Legal Limit | Status |
|---|---|---|---|---|
| Hardness (as CaCO₃) | 30 PPM | < 60 PPM | No federal limit | ✓ OK |
| Total Dissolved Solids | 52 PPM | < 300 PPM | 500 PPM | ✓ OK |
| PFAS (total) | 0 ppt | — | No total limit | ✓ ND |
| ↳ PFOA | 0 ppt | 0 ppt | 4 ppt (2024) | ✓ OK |
| ↳ PFOS | 0 ppt | 0 ppt | 4 ppt (2024) | ✓ OK |
| Lead | 9.4 ppb | 0 ppb (no safe level) | 15 ppb (10 ppb in 2027) | ⚠ Elevated |
| Chlorine / Chloramine | 1.6 mg/L | Taste threshold ~1.0 | 4.0 mg/L | ✓ Normal |
| Nitrate | 0.311 mg/L | 5 mg/L | 10 mg/L | ✓ OK |
Recommendations for Hilo Homes
Quick Fix for Chlorine: Shower Filter
At 1.6 mg/L chlorine, many Hilo residents notice dry skin, brittle hair, and that "pool smell" in the shower. A shower filter installs in 5 minutes, no tools needed.
How to Test Your Water in Hilo
Lead enters water from your home's plumbing, not the treatment plant — so Hilo's city-wide average of 9.4 ppb may not match your tap. Testing your specific faucet is the only way to know. Run cold water for 30 seconds before collecting a sample.
Free option: Request Hawaii County DWS's annual Consumer Confidence Report for official city-level data.
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About Hilo's Water Supply
Water Utility: Hawaii County DWS
Water Source: Wailuku River & wells (Groundwater)
Population Served: 39,477
Hardness: 30 PPM (1.8 grains per gallon)
Hilo draws its drinking water from groundwater sources — Wailuku River & wells. Groundwater typically requires less treatment than surface water because the earth acts as a natural filter. The tradeoff: dissolved minerals from underground rock formations, which is why mineral content varies by aquifer depth and geology. The geological profile determines hardness, iron, and trace mineral levels. The system serves 39,000 residents.
Water quality can vary by neighborhood and season. For your exact numbers, request Hawaii County DWS's Consumer Confidence Report (CCR) or test your own tap.
ZIP Codes Covered by This Report
This water quality data applies to all areas served by Hawaii County DWS in Hilo, HI, including ZIP codes:
96710, 96718, 96720, 96721, 96727, 96728, 96745, 96749, 96760, 96764, 96771, 96773, 96774, 96776, 96777, 96778, 96780, 96781, 96783, 96785
If your ZIP code is listed above, this report covers your water supply. Water quality may vary slightly by neighborhood.
Compare Hilo to Other Hawaii Cities
Frequently Asked Questions About Hilo Water
Is Hilo tap water safe to drink?
Where does Hilo's water come from?
Do I need a water softener in Hilo?
What water filter is best for Hilo?
Is Hilo water safe for babies and infants?
What are disinfection byproducts in Hilo's water?
Is chromium-6 in Hilo's water?
Why does Hilo water taste like chlorine?
Data sources: Lead and copper data from EPA Safe Drinking Water Act LCR reporting. Contaminant data from utility-reported testing results. PFAS data from EPA UCMR5 (2023–2025). Hardness from USGS and municipal reports. Data reflects system-level testing results and may not match your specific tap due to neighborhood plumbing, season, or recent utility changes. For your utility's latest results, request their Consumer Confidence Report (CCR). Our methodology. Last updated: 2026-02-24.
What Hilo Homeowners Actually Buy
Common purchases for homes with 30 PPM water.
Affiliate disclosure: we may earn a commission. Selection based on Hilo's water data.