Allegheny County, PA
drinking water quality
1,231,814 residents · 70 public water systems · 103 ZIP codes
EPA sampled 32 of 70 public water systems here, together serving about 1,976,992 people. The highest reading was PFOS at 18.8 ng/L at Coraopolis Water & Sewer Auth. 4 of the sampled systems were above a federal limit. Last sampled 9/6/2023.
What was found
| Compound | Highest result | Federal limit | Ratio |
|---|---|---|---|
| PFOS | 18.8 ng/L | 4 ng/L | 4.7× |
| PFOA | 5.2 ng/L | 4 ng/L | 1.3× |
| PFHxS | 12.6 ng/L | 10 ng/L | 1.3× |
Also detected, with no federal limit set: PFBS (14.6 ng/L), PFBA (6.2 ng/L), PFHxA (3.2 ng/L), PFPeA (3.1 ng/L).
Health-based violations
Separately from PFAS, EPA records 65 health-based violations across 21 of the county’s water systems since 2020, the most recent in 2026. They involved contaminant 0200, trihalomethanes, total coliform, contaminant 0700, haloacetic acids, lead and copper.
What this means
PFAS are industrial chemicals that EPA describes as breaking down only very slowly in the environment. In April 2024 EPA set the first enforceable national limits: 4 ng/L for PFOA and PFOS, 10 ng/L for PFHxS, PFNA and GenX.
These figures are county-level and come from EPA’s sampling of public water systems. They describe the worst result found in the county, not what comes out of any particular tap — that depends on which system serves the address, and on the plumbing in the building. A private well is not covered by this programme at all.
ZIP codes in Allegheny County
15006 · 15007 · 15014 · 15015 · 15017 · 15018 · 15020 · 15024 · 15025 · 15028 · 15030 · 15031 · 15034 · 15035 · 15037 · 15044 · 15045 · 15046 · 15047 · 15049 · 15051 · 15056 · 15064 · 15065 · 15071 · 15075 · 15076 · 15082 · 15084 · 15086 · 15088 · 15090 · 15101 · 15102 · 15104 · 15106 · 15108 · 15110 · 15112 · 15116 · 15120 · 15122 · 15123 · 15126 · 15129 · 15131 · 15132 · 15133 · 15135 · 15136 · 15137 · 15139 · 15140 · 15142 · 15143 · 15144 · 15145 · 15146 · 15147 · 15148 · 15201 · 15202 · 15203 · 15204 · 15205 · 15206 · 15207 · 15208 · 15209 · 15210 · 15211 · 15212 · 15213 · 15214 · 15215 · 15216 · 15217 · 15218 · 15219 · 15220 · 15221 · 15222 · 15223 · 15224 · 15225 · 15226 · 15227 · 15228 · 15229 · 15232 · 15233 · 15234 · 15235 · 15236 · 15237 · 15238 · 15239 · 15241 · 15243 · 15260 · 15275 · 15282 · 15290
Readings are county-level, so every ZIP here shares the figure above. Search your ZIP on the map to see it in context.