Is Caldwell, ID Tap Water Safe to Drink?
Yes, Caldwell tap water is safe to drink. Hardness is low at 70 PPM, and no contaminants exceed health guidelines. Most homes here don't need treatment.
Hardness Scale: Where Caldwell Falls
0Slightly
60Moderate
120Hard
180Very Hard
250Extreme
400+
How Caldwell Compares
Caldwell's water is 49% softer than the national average of 138 PPM - ranking in the bottom 64% for hardness nationwide. Most homes here do not need a softener. Within Idaho, it ranks #6 of 11 cities (4% below the state average of 73 PPM). Among cities (50k-100k), Caldwell ranks #182 of 258 for hardness.
What Caldwell's Water Means for Your Home
Hardness: 70 PPM - Low Concern
Caldwell's water is moderately hard at 70 PPM. You'll see some spotting on glassware and a film on shower doors over time, but it's not the kind of hardness that demands a full softener. The minerals come from the local aquifer geology. A salt-free conditioner is worth considering if you have a tankless water heater or high-end fixtures.
Contaminants & Safety
Lead levels deserve attention. At 5 ppb, Caldwell is above the ideal of zero, though below the EPA action level of 15 ppb (dropping to 10 ppb in November 2027 under the Lead and Copper Rule Improvements). The lead typically comes from aging service lines or interior plumbing, not the treatment plant. A point-of-use filter certified for lead at the kitchen faucet is a practical safeguard, especially in older homes.
What's in the Treatment Process
Chromium-6 is naturally present in Caldwell's aquifer geology at 3.08 ppb — 154x the EWG health guideline. There's no federal legal limit for chromium-6 specifically (only total chromium), which is why EWG tracks it separately. All measurements are within federal legal limits. The EWG guidelines represent a more conservative, health-based standard.
| Contaminant | Detected | Health Guideline | Legal Limit | Status |
|---|---|---|---|---|
| Hardness (as CaCO₃) | 70 PPM | < 60 PPM | No federal limit | ✓ OK |
| Total Dissolved Solids | 125 PPM | < 300 PPM | 500 PPM | ✓ OK |
| PFAS (total) | 0 ppt | — | No total limit | ✓ ND |
| ↳ PFOA | 0 ppt | 0 ppt | 4 ppt (2024) | ✓ OK |
| ↳ PFOS | 0 ppt | 0 ppt | 4 ppt (2024) | ✓ OK |
| Lead | 5 ppb | 0 ppb (no safe level) | 15 ppb (10 ppb in 2027) | ✓ Low |
| Chlorine / Chloramine | 0.7 mg/L | Taste threshold ~1.0 | 4.0 mg/L | ✓ Normal |
| Nitrate | 0.71 mg/L | 5 mg/L | 10 mg/L | ✓ OK |
Recommendations for Caldwell Homes
How to Test Your Water in Caldwell
Lead enters water from your home's plumbing, not the treatment plant — so Caldwell's city-wide average of 5 ppb may not match your tap. Testing your specific faucet is the only way to know. Run cold water for 30 seconds before collecting a sample.
Free option: Request City of Caldwell Water's annual Consumer Confidence Report for official city-level data.
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About Caldwell's Water Supply
Water Utility: City of Caldwell Water
Water Source: Surface water via Canyon County (Groundwater)
Population Served: 74,000
Hardness: 70 PPM (4.1 grains per gallon)
Caldwell draws its drinking water from groundwater sources — Surface water via Canyon County. Groundwater typically requires less treatment than surface water because the earth acts as a natural filter. The tradeoff: dissolved minerals from underground rock formations, which is why mineral content varies by aquifer depth and geology. The geological profile determines hardness, iron, and trace mineral levels. The system serves 74,000 residents.
Water quality can vary by neighborhood and season. For your exact numbers, request City of Caldwell Water's Consumer Confidence Report (CCR) or test your own tap.
ZIP Codes Covered by This Report
This water quality data applies to all areas served by City of Caldwell Water in Caldwell, ID, including ZIP codes:
83605, 83606, 83607, 83619, 83626, 83628, 83630, 83636, 83639, 83644, 83655, 83656, 83660, 83661, 83672, 83676, 97710, 97722, 97732, 97736, 97901, 97903, 97904, 97906, 97907, 97909, 97911, 97913, 97914, 97917, 97918, 97920
If your ZIP code is listed above, this report covers your water supply. Water quality may vary slightly by neighborhood.
Compare Caldwell to Other Idaho Cities
Frequently Asked Questions About Caldwell Water
Is Caldwell tap water safe to drink?
Where does Caldwell's water come from?
Do I need a water softener in Caldwell?
What is the hardness of Caldwell water in grains per gallon?
What are disinfection byproducts in Caldwell's water?
Is chromium-6 in Caldwell's water?
Can I drink Caldwell tap water straight from the faucet?
What water filter is best for Caldwell?
Data sources: Lead and copper data from EPA Safe Drinking Water Act LCR reporting. Contaminant data from utility-reported testing results. PFAS data from EPA UCMR5 (2023–2025). Hardness from USGS and municipal reports. Data reflects system-level testing results and may not match your specific tap due to neighborhood plumbing, season, or recent utility changes. For your utility's latest results, request their Consumer Confidence Report (CCR). Our methodology. Last updated: 2026-02-24.