Maricopa County, AZ
drinking water quality
4,673,096 residents · 217 public water systems · 135 ZIP codes
EPA sampled 42 of 217 public water systems here, together serving about 4,344,702 people. The highest reading was PFOS at 55.8 ng/L at Tempe City Of. 8 of the sampled systems were above a federal limit. Last sampled 9/9/2024.
What was found
| Compound | Highest result | Federal limit | Ratio |
|---|---|---|---|
| PFOS | 55.8 ng/L | 4 ng/L | 13.9× |
| PFOA | 38.7 ng/L | 4 ng/L | 9.7× |
| PFHxS | 70.5 ng/L | 10 ng/L | 7.0× |
Also detected, with no federal limit set: lithium (278000 ng/L), PFBS (25.7 ng/L), PFHxA (22.5 ng/L), PFPeA (14.4 ng/L), PFBA (9.9 ng/L).
Health-based violations
Separately from PFAS, EPA records 104 health-based violations across 55 of the county’s water systems since 2020, the most recent in 2026. They involved E. coli, nitrate, arsenic, total coliform, lead and copper, contaminant 0300.
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.
Find out what is in your own tap
This is a county-level reading from federal monitoring. What comes out of your own tap depends on your system — and on your home.
Allegiance Water Services is the water treatment provider listed for Maricopa County.
ZIP codes in Maricopa County
85003 · 85004 · 85006 · 85007 · 85008 · 85009 · 85012 · 85013 · 85014 · 85015 · 85016 · 85017 · 85018 · 85019 · 85020 · 85021 · 85022 · 85023 · 85024 · 85026 · 85027 · 85028 · 85029 · 85031 · 85032 · 85033 · 85034 · 85035 · 85037 · 85040 · 85041 · 85042 · 85043 · 85044 · 85045 · 85048 · 85050 · 85051 · 85053 · 85054 · 85083 · 85085 · 85086 · 85087 · 85201 · 85202 · 85203 · 85204 · 85205 · 85206 · 85207 · 85208 · 85209 · 85210 · 85212 · 85213 · 85215 · 85224 · 85225 · 85226 · 85233 · 85234 · 85236 · 85248 · 85249 · 85250 · 85251 · 85253 · 85254 · 85255 · 85256 · 85257 · 85258 · 85259 · 85260 · 85262 · 85263 · 85264 · 85266 · 85268 · 85281 · 85282 · 85283 · 85284 · 85286 · 85295 · 85296 · 85297 · 85298 · 85301 · 85302 · 85303 · 85304 · 85305 · 85306 · 85307 · 85308 · 85309 · 85310 · 85320 · 85322 · 85323 · 85326 · 85329 · 85331 · 85333 · 85335 · 85337 · 85338 · 85339 · 85340 · 85343 · 85345 · 85351 · 85353 · 85354 · 85355 · 85361 · 85363 · 85373 · 85374 · 85375 · 85377 · 85378 · 85379 · 85381 · 85382 · 85383 · 85387 · 85388 · 85390 · 85392 · 85395 · 85396 · 85545
Readings are county-level, so every ZIP here shares the figure above. Search your ZIP on the map to see it in context.