01The verdict: is Twin Rocks water safe?
Twin Rocks's drinking water has significant quality concerns based on EPA testing data. With a grade of D+ (52/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 1,650 residents using surface water (rivers, lakes, or reservoirs).
Lead is over its legal limit
Measured at 17.0 ppb against the EPA Action Level of 15 ppb. The ledger below shows how far over — and which filter removes it.
See the measurement ↓2K people, 1 system
All figures on this page come from federal EPA compliance and testing data for the systems serving this city.
See the systems ↓6 violations in the last five years
Recent compliance history is the best predictor of future problems — the year-by-year record is below.
See the record ↓Twin Rocks's drinking water received a grade of D+ (52 out of 100), indicating poor water quality. The city's 1 water system serves approximately 1,650 residents using purchased surface water.
Lead levels were measured at 17.0 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 47 violations on record, including 24 health-based violations. 14 remain unresolved.
Twin Rocks ranks #312 out of 559 cities in Pennsylvania for water quality, placing it below average 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. 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, Twin Rocks may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities. The system has seen 6 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
02What's in Twin Rocks's water
Every contaminant flagged in Twin Rocks, on one shared scale: distance to its own legal limit. The red line is the limit — anything past it is out of compliance, and the closer a bar gets, the less headroom the system has.
Over Limit — EPA Action Level: 15 ppb
Exceeds the EPA action level. Lead enters at the service line, not the treatment plant — your address matters more than the city average. Lead service line replacement and an NSF 53-certified point-of-use filter are recommended.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. | 17.0 | 15 | ppb | Inorganic | Over Limit |
Cities ranked by 90th-percentile lead PF PFAS in Pennsylvania
Cities ranked by compounds detected Cu Copper in Pennsylvania
Cities ranked by 90th-percentile copper
03Twin Rocks's ten-year track record
Each box is one year. A green check means no EPA violations; a numbered badge counts that year's violations — red if any were health-based, amber if they were monitoring or paperwork issues. The system has 47 violations on record, including 24 health-based violations. 14 remain unresolved.
3 of the last ten years were clean. The numbered years had EPA violations — red when any were health-based, amber when they were paperwork or missed-testing issues.
▼ Down 29 ppb since 2003. The latest reading (17 ppb, 2016) is over the action level. Sampled at higher-risk homes (90th percentile).
04Where Twin Rocks's water comes from
Twin Rocks's drinking water comes primarily from surface water sources such as rivers, lakes, or reservoirs.
Purchased Surface Water
Rivers, lakes, or reservoirs — more exposed to runoff, agriculture, and seasonal swings than groundwater.
Wholesale supplier
Multi-barrier treatment: coagulation, sedimentation, filtration, and disinfection to meet EPA standards.
1 system
1 water system, operated under local government ownership.
1,650 people
Residents served across Twin Rocks's service area.
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 1,650 people through 1 water system.
| System name | PWSID | Population | Source |
|---|---|---|---|
| BLACKLICK VALLEY MUNI AUTH | PA4110077 | 1,650 | Purchased Surface Water |
Water bodies near Twin Rocks
As a surface-water system, these water bodies may directly influence Twin Rocks's drinking water supply.
05Pressure on Twin Rocks's watershed
Outside forces that shape what reaches the treatment plant. None of these is a verdict on the tap by itself — but each adds pressure worth knowing about.
Industrial discharge
2 facilities within 10 miles reported 0 lb released to surface water in the latest EPA Toxics Release Inventory. Proximity doesn't equal tap contamination — treatment and hydrology decide — but it's pressure on the watershed.
Flood & storm history
8 federal disaster declarations on record for Cambria County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
06How Twin Rocks compares
Scores for nearby Pennsylvania cities on one line, with the average marked.
dashed line = Pennsylvania average (49/100)
Twin Rocks scores 52/100 — on par with the Pennsylvania average of 49/100. It outscores 8 of 10 nearby cities. Full Pennsylvania rankings →
79.8 / 100FBryn Mawr, PA
34.2 / 100FPittsburgh, PA
44 / 100AMcmurray, PA
86.8 / 100DGreensburg, PA
46.7 / 100FHarrisburg, PA
35.6 / 100
Compare all cities in the county — grades, violations, and contaminant data side by side.→
07What to do at home
Steps matched to what testing actually found in Twin Rocks's water — not generic advice.
Filter drinking & cooking water
NSF 53-certified pitcher or under-sink filter. Lead level (17.0 ppb) exceeds the EPA action level of 15 ppb
Compare tested filters →Flush taps & check your service line
Lead leaches from pipes as water sits. Run cold water 30 seconds before drinking (especially mornings), and ask the utility whether your address still has a lead service line.
Lead risks explained →Watch for Twin Rocks alerts
This area has a history of flood declarations — after severe weather, watch for boil-water advisories from the utility, and check the live alerts on this page.
All water alerts →Frequently asked questions
Is Twin Rocks, PA tap water safe to drink?
Twin Rocks's water quality earned a grade of D+ (52/100). Significant issues have been found. A water filter is strongly recommended. The city ranks #312 out of 559 cities tested in Pennsylvania.
What contaminants are in Twin Rocks's water?
Lead was measured at 17.0 ppb (90th percentile). 47 violations are on record.
How is Twin Rocks'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 Twin Rocks?
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 Twin Rocks's water come from?
Twin Rocks's water is sourced from Purchased surface water. The city has 1 water system serving approximately 1,650 residents.
What health violations has Twin Rocks's water system had?
Twin Rocks has 24 health-based violations on record. The most recent violation was recorded in November 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 14 violations remain unresolved.
How does Twin Rocks's water compare to other cities?
Twin Rocks ranks #312 out of 559 cities in Pennsylvania (better than 44% of state cities) and #12592 out of 15382 cities nationally (18th percentile). The grade of D+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Twin Rocks's small water system affect quality?
Twin Rocks's system serves approximately 1,650 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 47 violations on record.