Water Hardness in Hilo, Hawaii
The water hardness in Hilo, HI is 18 ppm (1.1 grains per gallon), which is classified as Soft . Water in Hilo is supplied by Hawaii County Department of Water Supply and comes primarily from surface water sources such as rivers, lakes, and reservoirs. No water softening treatment is needed. Hilo residents enjoy naturally soft water that is gentle on plumbing, appliances, and skin.
Water Quality Details for Hilo, HI
What 18 PPM Means for Your Home in Hilo
At 18 ppm, Hilo's water is classified as soft. This is excellent news for homeowners. Soft water lathers easily with soap and shampoo, leaves no mineral spots on dishes or glassware, and causes no scale buildup in your plumbing or water heater. Your appliances will operate at peak efficiency and enjoy their full expected lifespan. Laundry washed in soft water comes out cleaner and softer, and you will use significantly less soap, shampoo, and detergent than households with hard water. There is no need to invest in any water softening or conditioning equipment.
Water Source and Treatment at Hawaii County Department of Water Supply
Hilo's water is supplied by Hawaii County Department of Water Supply and sourced primarily from surface water bodies including rivers, lakes, and reservoirs. Surface water typically requires more treatment for biological contaminants (bacteria, algae, sediment) but tends to have lower mineral content than groundwater. The hardness level of 18 ppm in Hilo reflects the mineral content picked up as water flows through local watershed geology before reaching the treatment plant. The water has a pH of 6.8, which is slightly acidic, and total dissolved solids of 30 ppm (low).
Estimated Cost of Hard Water in Hilo
With soft water at 18 ppm, Hilo residents enjoy minimal costs associated with water hardness. There is no need for a water softener, and your appliances, plumbing, and fixtures will operate efficiently without mineral-related issues. You can use the manufacturer-recommended amounts of soap, shampoo, and detergent without needing extra.
Other Cities in Hawaii
Compare Hilo's water hardness with other cities in Hawaii. Water hardness can vary significantly within a state depending on local geology and water sources.
| City | Hardness (PPM) | GPG | Level | Source |
|---|---|---|---|---|
| Hilo | 18 ppm | 1.1 | Soft | Surface |
| Kailua-Kona | 85 ppm | 5 | Slightly Hard | Ground |
| Honolulu | 70 ppm | 4.1 | Slightly Hard | Ground |
| Pearl City | 65 ppm | 3.8 | Slightly Hard | Ground |
| Kailua | 55 ppm | 3.2 | Soft | Ground |
| Kaneohe | 48 ppm | 2.8 | Soft | Ground |
| Kahului | 30 ppm | 1.8 | Soft | Mixed |
| Lihue | 25 ppm | 1.5 | Soft | Surface |
Test Your Water for Accurate Results
The hardness value shown for Hilo (18 ppm) is based on the most recent available data from Hawaii County Department of Water Supply. Your actual water hardness may vary depending on your neighborhood, the age of your plumbing, and seasonal changes in water supply. For the most accurate measurement, we recommend testing your tap water with a home test kit or requesting a current water quality report from Hawaii County Department of Water Supply. Visit our hardness scale guide to understand what your test results mean, or explore all treatment solutions to find the right option for your home.