Severe PFAS contamination (Red Hill)Moderately hard
What Honolulu's Water Means for Your Home
Honolulu's water is moderately hard at 80 PPM. At this level, hard water is not a significant concern for most households. Scale buildup is minimal, and a water softener would provide little measurable benefit. If you are considering water treatment in Honolulu, focus on contaminant filtration rather than softening.
PFAS contamination is a significant concern in Honolulu. At 20 parts per trillion, levels exceed the EPA's 2024 maximum contaminant level of 4 ppt. PFAS are synthetic chemicals that do not break down in the environment or the human body, which is why they are called "forever chemicals." Long-term exposure has been associated with increased cancer risk, thyroid disruption, and immune system effects. A whole-house activated carbon filter or point-of-use reverse osmosis system can reduce PFAS to safe levels. Look for NSF P473 certification when comparing products.
Contaminant
Detected
Health Guideline
Legal Limit
Status
Hardness (as CaCO₃)
80 PPM
< 60 PPM
No federal limit
✓ OK
Total Dissolved Solids
140 PPM
< 300 PPM
500 PPM
✓ OK
PFAS (total)
20 ppt
4 ppt (EPA)
4 ppt (2024)
⚠ Above limit
Lead
1 ppb
0 ppb (no safe level)
15 ppb (action level)
✓ Low
Chlorine / Chloramine
1.3 mg/L
Taste threshold ~1.0
4.0 mg/L
✓ Normal
Nitrate
2 mg/L
5 mg/L
10 mg/L
✓ OK
Recommendations for Honolulu Homes
🔄Salt-Free Conditioner (Optional)
At 80 PPM, Honolulu's water is moderately hard. Scale buildup is slow but noticeable over years, especially in tankless water heaters. A salt-free conditioner is a low-maintenance option if you want to extend appliance life.
PFAS detected at 20 ppt, above the EPA maximum contaminant level of 4 ppt. PFAS are linked to cancer, thyroid disease, and immune system effects with long-term exposure. A whole-house granular activated carbon (GAC) filter or a point-of-use reverse osmosis system can reduce PFAS. Look for NSF P473 certification, which specifically tests for PFAS removal.
Water quality can vary by neighborhood and season. The values above represent typical averages reported by BWS Honolulu. To get exact numbers for your address, request a copy of the most recent Consumer Confidence Report (CCR) from your utility, or have your water independently tested.
Frequently Asked Questions About Honolulu Water
Is Honolulu tap water safe to drink?
Honolulu's water meets EPA legal standards for drinking water safety. However, legal limits and health-optimal levels are different things. PFAS levels exceed the 2024 EPA health standard, which is a concern for long-term exposure. Review the contaminant table above for specific numbers and how they compare to both legal limits and health guidelines.
Do I need a water softener in Honolulu?
At 80 PPM, Honolulu's water is moderately hard. Some homeowners at this level do not notice problems, while others see spotting on glassware, film on shower doors, or reduced soap lathering. Homes with tankless water heaters at this hardness level should strongly consider at least a salt-free conditioner, as scale buildup inside the heat exchanger can void the warranty. For other homes, it depends on your sensitivity and fixtures.
What water filter is best for Honolulu?
The best filter depends on which contaminants you want to address. For PFAS, look for a filter with NSF P473 certification. Granular activated carbon (GAC) and reverse osmosis systems are both effective. Standard carbon pitcher filters may not remove PFAS adequately. For chlorine taste and odor, an activated carbon filter is effective and affordable, available as under-sink, countertop, or whole-house systems. See our softener vs. filter guide to understand the difference between these categories.
Where does Honolulu's water come from?
Honolulu's drinking water is sourced from Groundwater (basalt aquifer) and treated by BWS Honolulu.
What is the hardness of Honolulu water in grains per gallon?
Honolulu's water hardness is undefined grains per gallon (GPG), which equals 80 parts per million (PPM). This is classified as moderately hard. To convert: 1 GPG = 17.1 PPM.
Does Honolulu water damage tankless water heaters?
At undefined GPG, Honolulu's water is unlikely to cause significant issues for tankless water heaters. However, if you notice reduced flow or efficiency over time, scale buildup could be a factor. Annual flushing with vinegar is good maintenance regardless of hardness.
Is Honolulu water safe for babies and infants?
Honolulu's water meets all EPA safety standards and is generally considered safe for preparing infant formula. The hardness minerals (calcium and magnesium) are not harmful. If your home has older plumbing, running cold water for 30 seconds before use is a good precaution to flush any lead from pipes.
Data sources. Water quality data compiled from EPA SDWIS, EWG Tap Water Database, USGS water hardness studies, and the BWS Honolulu Consumer Confidence Report. Hardness and contaminant levels represent typical average values and may vary by neighborhood and season. Last updated: 2026-02-12.