Holbrook Water Hardness & Quality Report (2026)
Water Hardness
9.7 grains per gallon
Source
reservoir
pH Level
8.2
neutral = 7.0
Lead
0.008 mg/L
✓ Below action level
TDS
427.3 mg/L
Est. Daily Cost
$0.44
energy & soap waste
Source: USGS Water Quality Portal · Updated 2026
0–60
mg/L
Soft
61–120
mg/L
Moderately Hard
121–180
mg/L
Hard
180+
mg/L
Very Hard
Appliance Damage Report
In Holbrook, your appliances are currently losing 22% efficiency due to mineral buildup.
| Appliance | In Holbrook | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 4.1 yrs | 8.5 yrs | -52% |
| Washing Machine | 7.4 yrs | 12 yrs | -38% |
| Water Heater | 8.9 yrs | 15 yrs | -41% |
Regional Water Comparison
How Holbrook compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Holbrook, New York | 166.5 mg/L | 8 ppt | 🟠 Hard | reservoir |
| Holtsville, New York | 174.5 mg/L | 8.3 ppt | 🟠 Hard | reservoir |
| Centereach, New York | 112.5 mg/L | 5.4 ppt | 🟡 Moderately Hard | reservoir |
| Farmingville, New York | 101 mg/L | 4.9 ppt | 🟡 Moderately Hard | reservoir |
| Lake Ronkonkoma, New York | 179 mg/L | 8.5 ppt | 🟠 Hard | reservoir |
National Benchmark
How Holbrook compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Holbrook | 166.5 mg/L | 🟠 Moderate |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Holbrook's Water Unique?
Local geology and source profile
Holbrook, New York, in Suffolk County — a major central Long Island suburban community (Holbrook is a significant Suffolk County hamlet — a central Long Island community in Islip Town adjacent to Ronkonkoma and Sayville; Holbrook is a classic post-WWII Suffolk County suburban hamlet that developed as part of the Long Island suburban expansion along the Southern State Parkway and Sunrise Highway corridors; Holbrook is adjacent to Ronkonkoma Lake (one of the most significant central Long Island kettle lakes — Lake Ronkonkoma, the deepest lake on Long Island, is adjacent to the Holbrook area) and is an important LIRR station stop on the Ronkonkoma branch (one of the busiest LIRR lines, serving the central Long Island commuter corridor)), a diverse Suffolk County community with a primarily Italian-American, working-class, and middle-class suburban Long Island population, adjacent to Ronkonkoma and Sayville in the central Suffolk County corridor — draws its municipal water supply via the Suffolk County Water Authority. Water hardness in Holbrook measures 166.5 mg/L — classified as hard.
Holbrook's hard supply reflects the central Suffolk County Long Island Magothy aquifer's calcareous-moderate character. The Magothy Aquifer at Holbrook draws from Cretaceous calcareous-moderate Magothy Sand with limited softening, producing the hard 166.5 mg/L.
At 166.5 mg/L, Holbrook residents face regular hard water challenges. Monthly descaling and water softeners are recommended. Suffolk County Water Authority consistently delivers water meeting all New York State DEC and EPA Safe Drinking Water Act requirements.
Geology & Source: Groundwater from the Upper Glacial and Magothy Aquifers via the Suffolk County Water Authority — the Suffolk County central Long Island Holbrook corridor (Cretaceous calcareous-moderate Magothy Sand — the calcareous-moderate central Suffolk County Long Island coastal plain aquifer; limited softening); hard supply at 166.5 mg/L in Suffolk County.