Is Mackay, ID Tap Water Safe to Drink?
Graded A, with 4 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
92.2/100
waterverge.com Mackay, ID — Water Quality Report
Mackay's drinking water received a grade of A (92.2 out of 100), indicating excellent water quality. The city's 1 water system serves approximately 566 residents using groundwater.
Lead levels were measured at 1.0 ppb (90th percentile), well within EPA limits. This system has not yet been tested for PFAS under the EPA UCMR 5 program.
The system has 31 violations on record, including 7 health-based violations. 4 remain unresolved.
What to know about Mackay's water
Mackay ranks #13 out of 139 cities in Idaho for water quality, placing it one of the best in the state.
Mackay relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff.
As a small community water system, Mackay may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Mackay, ID water safe to drink?
Mackay's drinking water has significant quality concerns based on EPA testing data. With a grade of A (92.2/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 566 residents using groundwater (wells).
Recent water quality updates for Mackay
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Mackay's water quality assessment. Grade: A (92.2/100).
Contaminants: Gross Alpha, Excl. Radon and U, Radium-226, Radium-228.
Federal disaster declaration (FEMA DR-4333). Flood event — may have impacted local water infrastructure.
1 health-based. Contaminants: Coliform (TCR).
1 health-based. Contaminants: Coliform (TCR).
Federal disaster declaration (FEMA DR-3244). Hurricane event — may have impacted local water infrastructure.
Key contaminant findings
Based on the most recent EPA sampling data for Mackay's water supply.
Well within EPA limits.
Violation history
Mackay's water system has 31 total violations on record, including 7 health-based violations. 4 remain unresolved.
Flood & environmental risk
Custer County has experienced 2 federally declared disasters since 2005. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies. Local water sources include Mackay Res Nr Mackay, Big Lost River Bl Mackay Res Nr Mackay, Lower Cedar Creek Ab Divs Nr Mackay, Big Lost River Nr Leslie.
Where does Mackay's water come from?
Mackay's drinking water comes from groundwater (wells), supplied by 1 water system serving approximately 566 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Mackay Res Nr Mackay (lake), Big Lost River Bl Mackay Res Nr Mackay (river), Lower Cedar Creek Ab Divs Nr Mackay (river), Big Lost River Nr Leslie (river).
What Mackay residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Mackay's water.
Your water utility is required to publish an annual Consumer Confidence Report (CCR) with detailed testing results. Ask for the latest copy or check your utility's website.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Violation summary
Violations & advisories
Drought conditions
D1 — moderate droughtCuster County is currently in D1 (moderate drought) per the U.S. Drought Monitor (week of May 5, 2026). Drought can elevate disinfection-byproduct (TTHM/HAA5) levels and taste/odor issues as utilities draw from lower reservoirs.
Source: U.S. Drought Monitor, updated weekly by NDMC, USDA, and NOAA.
Flood & disaster history
Custer County has experienced 2 federally declared disasters since 2005. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 1.0 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how Mackay compares by contaminant
Explore where Mackay ranks among all Idaho cities for specific contaminants.
Water source & infrastructure
Where Mackay's water comes from
Mackay's drinking water is drawn from underground aquifers through wells.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals.
Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds.
The system is operated by local government ownership and serves approximately 566 people through 1 water system.
Water bodies near Mackay
Mackay is located near 4 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Mackay
| System Name | PWSID | Population | Source |
|---|---|---|---|
| MACKAY CITY OF | ID7190032 | 566 | GW |
How Mackay compares
Full Idaho rankings →Mackay's score of 92.2/100 is above the average of 43/100 among major Idaho cities. It outscores 10 of 10 nearby cities.
Nearby cities
View Idaho rankings →About Mackay, ID
Wikipedia →Mackay is a town in Custer County, Idaho, United States. The population was 439 at the 2020 census. The town is pronounced "Mackie" with the accent on the first syllable.
Learn more about your water
Guides and resources related to Mackay's water quality findings.
Explore water quality across Custer
Frequently asked questions
Is Mackay, ID tap water safe to drink?
Mackay's water quality earned a grade of A (92.2/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #13 out of 139 cities tested in Idaho.
What contaminants are in Mackay's water?
Lead was measured at 1.0 ppb (90th percentile). 31 violations are on record.
How is Mackay's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Mackay?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Mackay's water come from?
Mackay's water is sourced from Groundwater. The city has 1 water system serving approximately 566 residents.
What health violations has Mackay's water system had?
Mackay has 7 health-based violations on record. The most recent violation was recorded in January 2018. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 4 violations remain unresolved.
Is Mackay's groundwater at risk of contamination?
Mackay uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 31 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Mackay's water compare to other cities?
Mackay ranks #13 out of 139 cities in Idaho (better than 91% of state cities) and #1356 out of 15744 cities nationally (91th percentile). The grade of A reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Mackay's small water system affect quality?
Mackay's system serves approximately 566 residents. Small community water systems (under 3,300 people) may have fewer financial resources for infrastructure upgrades and advanced treatment technologies. However, they are held to the same EPA drinking water standards as larger systems. This system has 31 violations on record.