Is San Antonio, MP Tap Water Safe to Drink?
Graded D+ — but Lead was detected above EPA limits. Here's what's in the water and how to remove it. What to do next ↓
50.9/100
waterverge.com San Antonio, MP — Water Quality Report
San Antonio's drinking water received a grade of D+ (50.9 out of 100), indicating poor water quality. The city's 3 water systems serve approximately 848 residents using groundwater.
Lead levels were measured at 54.0 ppb (90th percentile), which exceeds the EPA action level of 15 ppb. This system has not yet been tested for PFAS under the EPA UCMR 5 program.
The system has 62 violations on record, including 20 health-based violations. 22 remain unresolved.
What to know about San Antonio's water
San Antonio ranks #4 out of 7 cities in Northern Mariana Islands for water quality, placing it mid-range in the state.
San Antonio 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.
Lead levels exceed the EPA action level of 15 ppb, which typically indicates aging lead service lines or lead solder in the distribution system. An NSF 53-certified filter is strongly recommended for drinking and cooking water.
As a small community water system, San Antonio may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
The system has seen 14 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
Water quality score
See methodology →Is San Antonio, MP water safe to drink?
San Antonio's drinking water has significant quality concerns based on EPA testing data. With a grade of D+ (50.9/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 3 water systems serve approximately 848 residents using groundwater (wells).
Recent water quality updates for San Antonio
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into San Antonio's water quality assessment. Grade: D+ (50.9/100).
Contaminants: Revised Total Coliform Rule.
Contaminants: Nitrate, TTHM, Total Haloacetic Acids (HAA5).
4 health-based. Contaminants: Groundwater Rule.
Key contaminant findings
Based on the most recent EPA sampling data for San Antonio's water supply.
Exceeds EPA action level. Lead service line replacement and point-of-use filtration recommended.
Violation history
San Antonio's water system has 62 total violations on record, including 20 health-based violations. 22 remain unresolved. 14 violations were issued in the last 5 years.
Where does San Antonio's water come from?
San Antonio's drinking water comes from groundwater (wells), supplied by 3 water systems serving approximately 848 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate.
What San Antonio residents can do
Recommended: NSF 53-certified pitcher or under-sink filter. This addresses the specific contaminants found in San Antonio'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.
Run cold water for 30 seconds before drinking, especially in the morning. Lead and copper leach from household plumbing when water sits in pipes.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Violation summary
Violations & advisories
Recommended water filters
Based on contaminants detected in San Antonio's water supply, we recommend the following filter types.
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. | 54.0 | 15 | ppb | Inorganic | Over Limit |
Lead level trend (90th percentile)
See how San Antonio compares by contaminant
Explore where San Antonio ranks among all Northern Mariana Islands cities for specific contaminants.
Water source & infrastructure
Where San Antonio's water comes from
San Antonio'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 private ownership and serves approximately 848 people through 3 water systems.
Water systems serving San Antonio
| System Name | PWSID | Population | Source |
|---|---|---|---|
| Pacific Islands Club | MP0000012 | 554 | GW |
| Aqua Water | MP0000177 | 170 | GW |
| Winners Residence | MP0000005 | 124 | GW |
How San Antonio compares
Full Northern Mariana Islands rankings →San Antonio's score of 50.9/100 is below the average of 60/100 among major Northern Mariana Islands cities. It outscores 3 of 6 nearby cities.
Nearby cities
View Northern Mariana Islands rankings →About San Antonio, MP
Wikipedia →Saipan is the largest island and capital of the Northern Mariana Islands, an unincorporated territory of the United States in the western Pacific Ocean. According to 2020 estimates by the United States Census Bureau, the population of Saipan was 43,385. Its people have been United States citizens since the 1980s. Saipan is one of the main homes of the Chamorro and the Carolinian, the indigenous people of the Mariana Islands.
Learn more about your water
Guides and resources related to San Antonio's water quality findings.
Frequently asked questions
Is San Antonio, MP tap water safe to drink?
San Antonio's water quality earned a grade of D+ (50.9/100). Significant issues have been found. A water filter is strongly recommended. The city ranks #4 out of 7 cities tested in Northern Mariana Islands.
What contaminants are in San Antonio's water?
Lead was measured at 54.0 ppb (90th percentile). 62 violations are on record.
How is San Antonio'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 San Antonio?
Yes — lead levels exceed the EPA action level of 15 ppb. We recommend an NSF 53-certified filter or reverse osmosis system. Based on current data, basic filtration should suffice for additional peace of mind.
Where does San Antonio's water come from?
San Antonio's water is sourced from Groundwater. The city has 3 water systems serving approximately 848 residents.
What health violations has San Antonio's water system had?
San Antonio has 20 health-based violations on record. The most recent violation was recorded in February 2023. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 22 violations remain unresolved.
Is San Antonio's groundwater at risk of contamination?
San Antonio 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 62 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 San Antonio's water compare to other cities?
San Antonio ranks #4 out of 7 cities in Northern Mariana Islands (better than 43% of state cities) and #12958 out of 15744 cities nationally (18th percentile). The grade of D+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.