Is Las Marias, PR Tap Water Safe to Drink?
Graded D, with 15 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
46.8/100
waterverge.com Las Marias, PR — Water Quality Report
Las Marias's drinking water received a grade of D (46.8 out of 100), indicating poor water quality. The city's 2 water systems serve approximately 7,193 residents using surface water.
Lead levels were measured at 6.0 ppb (90th percentile), which is within EPA limits but above recommended levels. PFAS testing under UCMR 5 found no detectable forever chemicals.
The system has 475 violations on record, including 54 health-based violations. 15 remain unresolved.
What to know about Las Marias's water
Las Marias ranks #47 out of 101 cities in Puerto Rico for water quality, placing it mid-range in the state.
The city draws from surface water sources, which are more susceptible to seasonal runoff and agricultural contamination, requiring extensive multi-barrier treatment including coagulation, filtration, and disinfection.
Haloacetic acid (HAA5) levels were elevated at 31.5 µg/L in UCMR 4 testing, though below the 60 µg/L EPA limit. Activated carbon filtration can help reduce these disinfection byproducts.
While lead levels are within EPA limits, they are above the recommended 5 ppb threshold that health organizations consider ideal. A point-of-use filter adds an extra layer of protection.
The system has seen 40 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
Water quality score
See methodology →Is Las Marias, PR water safe to drink?
Las Marias's drinking water has significant quality concerns based on EPA testing data. With a grade of D (46.8/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 2 water systems serve approximately 7,193 residents using surface water (rivers, lakes, or reservoirs).
Recent water quality updates for Las Marias
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Las Marias's water quality assessment. Grade: D (46.8/100).
Contaminants: Revised Total Coliform Rule.
Contaminants: Revised Total Coliform Rule.
Contaminants: Revised Total Coliform Rule.
Key contaminant findings
Based on the most recent EPA sampling data for Las Marias's water supply.
Within EPA limits but above the American Academy of Pediatrics recommended level of 1 ppb. An NSF 53-certified filter provides additional protection.
Violation history
Las Marias's water system has 475 total violations on record, including 54 health-based violations. 15 remain unresolved. 40 violations were issued in the last 5 years.
Where does Las Marias's water come from?
Las Marias's drinking water comes from surface water (rivers, lakes, or reservoirs), supplied by 2 water systems serving approximately 7,193 people. Surface water sources are more susceptible to contamination from runoff, industrial discharge, and algal blooms, requiring extensive treatment. Nearby water bodies include Rio De Bayamon Nr Bayamon (river), Quebrada Santa Catalina (river), Las Casas Lake (lake), Unnamed Creek (river), Rio Piedras (river).
What Las Marias residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Las Marias'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 ↓Forever chemicals overview
National PFAS report →Violation summary
Violations & advisories
Recommended water filters
Based on contaminants detected in Las Marias'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. | 6.0 | 15 | ppb | Inorganic | Safe |
| 11Cl-PF3OUdS | ND | HI | µg/L | PFAS | Not Detected |
| 4:2 FTS | ND | HI | µg/L | PFAS | Not Detected |
| 6:2 FTS 6:2 FTSPFAS A fluorotelomer sulfonate commonly found at sites contaminated with aqueous film-forming foam (AFFF) used in firefighting. Health EffectsPotential liver toxicity and endocrine disruption. Less studied but identified as a contaminant of concern. EPA LimitNo individual MCL (not yet regulated) Common SourcesFirefighting foam (AFFF), airports, military bases, and industrial facilities. | ND | HI | µg/L | PFAS | Not Detected |
| 8:2 FTS | ND | HI | µg/L | PFAS | Not Detected |
| 9Cl-PF3ONS | ND | HI | µg/L | PFAS | Not Detected |
| ADONA | ND | HI | µg/L | PFAS | Not Detected |
| HFPO-DA HFPO-DA (GenX)PFAS A replacement for PFOA in manufacturing, marketed as safer but still a persistent "forever chemical." Also known as GenX. Health EffectsLiver and kidney effects, reproductive toxicity, immune system effects, and potential cancer risk. EPA Limit10 ppt MCL Common SourcesFluoropolymer manufacturing (used as PFOA replacement), industrial wastewater discharge. | ND | 0.01 | µg/L | PFAS | Not Detected |
| lithium LithiumInorganic A naturally occurring alkali metal found in groundwater. Monitored under UCMR 5 to assess occurrence in drinking water. Health EffectsKidney effects at high doses. Low-level exposure effects under study; some research suggests neurological effects. EPA LimitNo MCL (monitoring only under UCMR 5) Common SourcesNatural mineral deposits, geothermal water, and industrial discharge. | ND | HI | µg/L | PFAS | Not Detected |
| NEtFOSAA | ND | HI | µg/L | PFAS | Not Detected |
| NFDHA | ND | HI | µg/L | PFAS | Not Detected |
| NMeFOSAA | ND | HI | µg/L | PFAS | Not Detected |
| PFBA PFBAPFAS One of the shortest-chain PFAS compounds. Very mobile in water and difficult to remove with standard filtration. Health EffectsThyroid effects, potential developmental toxicity. Shorter half-life in body than long-chain PFAS. EPA LimitNo individual MCL (not yet regulated) Common SourcesDegradation of longer-chain PFAS, industrial discharge, and firefighting foam. | ND | HI | µg/L | PFAS | Not Detected |
| PFBS PFBSPFAS A short-chain PFAS used as a replacement for PFOS. While it clears the body faster than long-chain PFAS, it still persists in the environment. Health EffectsThyroid effects, reproductive and developmental toxicity, kidney effects. EPA LimitPart of Hazard Index (1.0) Common SourcesIndustrial discharge, firefighting foam, and as a replacement chemical in manufacturing. | ND | HI | µg/L | PFAS | Not Detected |
| PFDA | ND | HI | µg/L | PFAS | Not Detected |
| PFDoA | ND | HI | µg/L | PFAS | Not Detected |
| PFEESA | ND | HI | µg/L | PFAS | Not Detected |
| PFHpA PFHpAPFAS A medium-chain PFAS compound found in various environmental samples. Less studied than PFOA/PFOS but still considered a contaminant of concern. Health EffectsLiver effects, potential developmental toxicity, and endocrine disruption. EPA LimitPart of Hazard Index (1.0) Common SourcesDegradation of longer-chain PFAS, industrial discharge, and contaminated water sources. | ND | HI | µg/L | PFAS | Not Detected |
| PFHpS | ND | HI | µg/L | PFAS | Not Detected |
| PFHxA PFHxAPFAS A short-chain PFAS replacement chemical widely used after manufacturers phased out longer-chain PFAS. Very commonly detected in water. Health EffectsLiver and kidney effects, potential thyroid disruption. Considered less toxic than long-chain PFAS but still persistent. EPA LimitNo individual MCL (not yet regulated) Common SourcesIndustrial processes, firefighting foam (AFFF), food packaging, and textile treatment. | ND | HI | µg/L | PFAS | Not Detected |
| PFHxS PFHxSPFAS A medium-chain PFAS found in firefighting foam and consumer products. It has a long half-life in the human body, similar to long-chain PFAS. Health EffectsImmune system effects, thyroid disruption, and potential reproductive and developmental harm. EPA LimitPart of Hazard Index (1.0) Common SourcesFirefighting foam (AFFF), waterproof textiles, food packaging, and industrial discharge. | ND | HI | µg/L | PFAS | Not Detected |
| PFMBA | ND | HI | µg/L | PFAS | Not Detected |
| PFMPA | ND | HI | µg/L | PFAS | Not Detected |
| PFNA PFNAPFAS A long-chain PFAS compound used in manufacturing fluoropolymers. It bioaccumulates in the body and is very persistent in the environment. Health EffectsDevelopmental effects, liver toxicity, immune suppression, and potential cancer risk. EPA LimitPart of Hazard Index (1.0) Common SourcesFluoropolymer manufacturing, industrial emissions, and contaminated water sources. | ND | HI | µg/L | PFAS | Not Detected |
| PFOA PFOAPFAS A long-chain PFAS ("forever chemical") once widely used in nonstick coatings and firefighting foam. It persists in the body and environment for years. Health EffectsLinked to kidney and testicular cancer, thyroid disease, elevated cholesterol, and reproductive issues. EPA Limit4.0 ppt MCL Common SourcesIndustrial discharge, firefighting foam (AFFF), nonstick cookware manufacturing, and contaminated groundwater. | ND | 0.004 | µg/L | PFAS | Not Detected |
| PFOS PFOSPFAS A long-chain PFAS compound historically used in stain-resistant coatings and firefighting foam. One of the most studied and persistent PFAS chemicals. Health EffectsLiver damage, immune system suppression, thyroid disruption, increased cholesterol, and potential cancer risk. EPA Limit4.0 ppt MCL Common SourcesFirefighting foam (AFFF), industrial sites, stain-resistant fabric treatments, and contaminated groundwater. | ND | 0.004 | µg/L | PFAS | Not Detected |
| PFPeA PFPeAPFAS A short-chain PFAS compound commonly detected in drinking water. One of the most frequently found PFAS in UCMR 5 monitoring. Health EffectsLess studied than PFOA/PFOS. Potential liver and thyroid effects. Research is ongoing. EPA LimitNo individual MCL (not yet regulated) Common SourcesIndustrial discharge, firefighting foam degradation, and consumer products. | ND | HI | µg/L | PFAS | Not Detected |
| PFPeS | ND | HI | µg/L | PFAS | Not Detected |
| PFTA | ND | HI | µg/L | PFAS | Not Detected |
| PFTrDA | ND | HI | µg/L | PFAS | Not Detected |
| PFUnA | ND | HI | µg/L | PFAS | Not Detected |
Lead level trend (90th percentile)
See how Las Marias compares by contaminant
Explore where Las Marias ranks among all Puerto Rico cities for specific contaminants.
Water source & infrastructure
Where Las Marias's water comes from
Las Marias's drinking water comes primarily from surface water sources such as rivers, lakes, or reservoirs.
Surface water systems require multi-stage treatment including coagulation, sedimentation, filtration, and disinfection to meet EPA Safe Drinking Water Act standards.
These sources can be impacted by seasonal changes, stormwater runoff, upstream agriculture, and industrial discharge.
The system is operated by local government ownership and serves approximately 7,193 people through 2 water systems.
Water bodies near Las Marias
Las Marias is located near 5 notable water bodies. As a surface water system, these water bodies may directly influence the city's drinking water supply.
Water systems serving Las Marias
| System Name | PWSID | Population | Source |
|---|---|---|---|
| LAS MARIAS | PR0003363 | 7,166 | SW |
| SECTOR LAGUNA | PR0377023 | 27 | SW |
How Las Marias compares
Full Puerto Rico rankings →Las Marias's score of 46.8/100 is above the average of 38/100 among major Puerto Rico cities. It outscores 10 of 10 nearby cities.
Nearby cities
View Puerto Rico rankings →Learn more about your water
Guides and resources related to Las Marias's water quality findings.
Explore water quality across Las Marias Municipio
Frequently asked questions
Is Las Marias, PR tap water safe to drink?
Las Marias's water quality earned a grade of D (46.8/100). Significant issues have been found. A water filter is strongly recommended. The city ranks #47 out of 101 cities tested in Puerto Rico.
What contaminants are in Las Marias's water?
Lead was measured at 6.0 ppb (90th percentile). No PFAS compounds were detected. 475 violations are on record.
How is Las Marias'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 Las Marias?
While lead levels are within EPA limits, a filter adds extra protection. Based on current data, basic filtration should suffice for additional peace of mind.
Where does Las Marias's water come from?
Las Marias's water is sourced from Surface water. The city has 2 water systems serving approximately 7,193 residents.
What health violations has Las Marias's water system had?
Las Marias has 54 health-based violations on record. The most recent violation was recorded in December 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 15 violations remain unresolved.
How does Las Marias's water compare to other cities?
Las Marias ranks #47 out of 101 cities in Puerto Rico (better than 53% of state cities) and #13837 out of 15744 cities nationally (12th percentile). The grade of D reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.