Lake Ronkonkoma Water Hardness & Quality Report (2026)
Water Hardness
10.5 grains per gallon
Source
reservoir
pH Level
8.3
neutral = 7.0
Lead
0.009 mg/L
✓ Below action level
TDS
482.1 mg/L
Est. Daily Cost
$0.48
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 Lake Ronkonkoma, your appliances are currently losing 24% efficiency due to mineral buildup.
| Appliance | In Lake Ronkonkoma | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 3.7 yrs | 8.5 yrs | -56% |
| Washing Machine | 7 yrs | 12 yrs | -42% |
| Water Heater | 8.4 yrs | 15 yrs | -44% |
Regional Water Comparison
How Lake Ronkonkoma compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Lake Ronkonkoma, New York | 179 mg/L | 8.5 ppt | 🟠 Hard | reservoir |
| Ronkonkoma, New York | 70.5 mg/L | 3.4 ppt | 🟡 Moderately Hard | reservoir |
| Nesconset, New York | 153.5 mg/L | 7.3 ppt | 🟠 Hard | reservoir |
| Centereach, New York | 112.5 mg/L | 5.4 ppt | 🟡 Moderately Hard | reservoir |
| Saint James, New York | 109.5 mg/L | 5.3 ppt | 🟡 Moderately Hard | reservoir |
National Benchmark
How Lake Ronkonkoma compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Lake Ronkonkoma | 179 mg/L | 🟠 Moderate |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Lake Ronkonkoma's Water Unique?
Local geology and source profile
Lake Ronkonkoma, New York, in Suffolk County — a central Suffolk County community named for Lake Ronkonkoma (a large glacial kettle lake — one of Long Island's largest natural freshwater lakes) in the Town of Brookhaven and Town of Islip — receives its municipal water from the Suffolk County Water Authority (SCWA), which draws from the Upper Glacial Aquifer (Pleistocene outwash) and the Magothy Aquifer (Cretaceous coastal plain sand) through SCWA wells in central Suffolk County.
The moderately hard 179 mg/L hardness and elevated TDS of 482.1 mg/L are consistent with the central Suffolk County SCWA supply zones — harder than North Shore zones (East Northport 174 mg/L) due to deeper reliance on the mineralized Magothy Aquifer in central Long Island. The Magothy Formation (Cretaceous fluvial and coastal plain sand) in central Suffolk has extended groundwater residence times, producing more mineralized water than the shallower Upper Glacial Aquifer zones used in the more northerly SCWA zones. The elevated TDS (482 mg/L) reflects sodium chloride contributions from Long Island's saltwater intrusion history and iron-manganese from the organic-rich Magothy sediment.
At 179 mg/L, Lake Ronkonkoma's water is moderately hard — scale builds in kettles and appliances over months, dishwashers benefit from rinse aid, and faucet aerators need periodic cleaning. Quarterly descaling is appropriate. The PFAS level of 8.5 ppt warrants a certified drinking water filter — the Grumman Bethpage PFAS plume (Cretaceous Magothy aquifer PFAS contamination from the former Grumman Aviation plant), Republic Airport (Farmingdale), and the Long Island Sound military-aviation corridor all contribute to SCWA central Suffolk County PFAS readings.
Geology & Source: Lake Ronkonkoma in Suffolk County draws from Suffolk County Water Authority (SCWA) on the Upper Glacial Aquifer and Magothy Aquifer — the Long Island aquifer system in central Suffolk County accesses Pleistocene outwash and Cretaceous Magothy Formation calcareous sand — Long Island Pleistocene outwash and Cretaceous coastal plain aquifer produces moderately hard water at 179 mg/L with elevated TDS 482 mg/L in this Suffolk County New York community.