Post Falls Water Hardness & Quality Report (2026)
Water Hardness
~120–179 mg/L
Hardestimated · not lab-verified
Source
groundwater
pH Level
7.3
neutral = 7.0
Lead
0.003 mg/L
✓ Below action level
TDS
28 mg/L
Est. Daily Cost
$0.40
energy & soap waste
Source: See methodology section below · 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 Post Falls, your appliances are currently losing 20% efficiency due to mineral buildup.
| Appliance | In Post Falls | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 6.8 yrs | 8.5 yrs | -20% |
| Washing Machine | 9.6 yrs | 12 yrs | -20% |
| Water Heater | 12 yrs | 15 yrs | -20% |
Regional Water Comparison
How Post Falls compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Post Falls, Idaho | ≈ 120–179 mg/L | 0 ppt | 🟠 Hard | groundwater |
| Hayden, Idaho | ≈ 120–179 mg/L | 0 ppt | 🟠 Hard | groundwater |
| Coeur d'Alene, Idaho | 152.67 mg/L | 0 ppt | 🟠 Hard | groundwater |
| Spokane Valley, Washington | ≈ 180+ mg/L | 0 ppt | 🔴 Very Hard | groundwater |
| Opportunity, Washington | ≈ 120–179 mg/L | 1.9 ppt | 🟠 Hard | reservoir |
National Benchmark
How Post Falls compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Post Falls | ≈ 120–179 mg/L | 🟠 Moderate |
| USA National Avg | 151 mg/L | 🟠 Moderate |
| Scarsdale Top Rated | 0.02 mg/L | 🟢 None |
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What Makes Post Falls's Water Unique?
Local geology and source profile
The City of Post Falls Water Division serves approximately 40,000 residents in Kootenai County, Idaho, primarily within the city limits and adjacent areas. Water is sourced exclusively from 14 municipal wells tapping the Rathdrum Prairie Aquifer — no surface water reservoirs or rivers are used. Treatment involves chlorination at wellheads for disinfection, basic filtration, and pH adjustment as needed. There are no centralized named treatment plants; all facilities are decentralized well stations. The service area is supplied entirely from this single groundwater source.
The Rathdrum Prairie Aquifer is part of the larger Spokane Valley–Rathdrum Prairie Aquifer system and the broader Columbia Plateau Aquifer. Water infiltrates through highly permeable glacial outwash plains of Quaternary age and fractured Miocene Columbia River Basalts, picking up calcium and magnesium from volcanic minerals and limestone-dolomite fragments within these layers. The permeable gravel aquifer over impermeable basalt promotes prolonged mineral dissolution, producing a hard supply with notable dissolved mineral content reflecting the region's volcanic history and glacial depositional legacy.
Hard water in Post Falls causes limescale buildup in pipes, water heaters, dishwashers, and washing machines, reducing efficiency and lifespan. Soap lathering is poor, leaving spots on dishes and contributing to skin dryness. Recommended maintenance includes flushing water heaters every 6–12 months, vinegar cleaning of fixtures, and installing a water softener for whole-house protection. The 2023 Consumer Confidence Report shows non-detects for PFAS and lithium, with lead levels at 1.9 ppb in 2019 — well below the 15 ppb action level. pH falls within the normal 6.5–8.5 range, and no notable violations for copper or other contaminants have been recorded.
Geology & Source: Rathdrum Prairie Aquifer; unconsolidated Quaternary glacial outwash — sands, gravels, silts — overlying Miocene Columbia River Basalt Group; calcium and magnesium-bearing minerals in basalt and limestone-dolomite fragments dissolve into groundwater,
Other Idaho Water Reports
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Frequently Asked Questions
Is Post Falls's water safe to drink?
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How does Post Falls compare to the USA average?
Data Sources & Methodology
Water quality data for Post Falls is derived from geographic and geological modelling of the surrounding region. No federal monitoring station data was available for this location.
Water Hardness
Modelled estimate based on state-level USGS geological survey data for this region. No direct USGS Water Quality Portal measurement was matched to this city — the value reflects a statistical range calibrated to the state's dominant rock types and typical source water characteristics.
pH
Estimated from regional geology and source water characteristics. pH is correlated with water hardness and local bedrock — values may differ from utility-reported figures.
TDS — Total Dissolved Solids
Estimated using a derived ratio from water hardness and regional conductance profiles. TDS in natural water correlates strongly with total mineral content including hardness ions.
PFAS — Perfluoroalkyl and Polyfluoroalkyl Substances
EPA UCMR5 (5th Unregulated Contaminant Monitoring Rule, 2023–2025) — sum of PFAS compounds detected at the public water system serving this city. A value of 0 indicates the system was sampled with no detection above reporting limits.
Lead
Modelled estimate based on the EPA Lead and Copper Rule 90th-percentile tap-sample methodology. No publicly available per-city lead dataset with sufficient national coverage exists. Values are a conservative baseline derived from city population tier and infrastructure age — all estimates are maintained below the EPA action level of 0.015 mg/L.
Appliance Lifespan
Calculated from water hardness using a linear degradation model. Baseline lifespans represent soft-water performance (kettle: 8.5 yrs, washing machine: 12.0 yrs, water heater: 15.0 yrs). Hard water mineral scale progressively reduces operational life in direct proportion to hardness concentration.