Maricopa County, AZ
These figures come from wells tested in Maricopa County, AZ, not from any one well.
- Sulfate is common in wells in Maricopa County, AZ (542 of 2151 tested wells were over that level), so it's worth testing for.
- Iron and manganese are not common in wells in Maricopa County, AZ (6 of 301 and 12 of 305 tested wells were over). Only a test tells you about your own well.
- Wells in Maricopa County, AZ are typically very hard (2275 wells tested).
- Only a test of your own well tells you about your water.
What to test for
Start with the four this site covers:
- sulfate (common in wells here)
- iron
- manganese
- hardness
Most well owners also test for these. We point to the source and don't interpret the results.
- arsenic: occurs naturally in groundwater in many regions. USGS: arsenic and drinking water
- nitrate: common near farmland and septic systems. EPA: private drinking water wells
- total coliform bacteria: the standard yearly well check. EPA: private drinking water wells
- lead and copper: from household plumbing, especially when pH is below 6.5. EPA: lead in drinking water
- PFAS: several states run private-well sampling programs. EPA: PFAS
- a certified lab: states certify labs and some run their own private-well programs. Arizona's certified-lab list (from your state drinking-water program)
The numbers
County figures describe the wells sampled there, not any one well. Exact counts, sample years and sources are below.
Iron Recent
| Level it's compared with | 0.3 mg/L |
|---|---|
| Share of wells over the level | 2.0% |
| Wells over the level / wells judged | 6 of 301 |
| Median | < DL mg/L |
| Years sampled | 1946–2024 |
| Wells | 301 |
| Test results | 2,290 |
| Wells left out | 342 |
| Sources | USGS (1,008), AZDEQ_GW (212), 21ARIZGW (148), SRPMIC_WQX (1) |
More than half the wells had results below the lab's detection limit, so the median is reported as below that limit.
Manganese Recent
| Level it's compared with | 0.05 mg/L |
|---|---|
| Share of wells over the level | 3.9% |
| Wells over the level / wells judged | 12 of 305 |
| Median | < 0.5 mg/L |
| Years sampled | 1957–2024 |
| Wells | 305 |
| Test results | 2,115 |
| Wells left out | 302 |
| Sources | USGS (880), AZDEQ_GW (209), 21ARIZGW (133), SRPMIC_WQX (6) |
More than half the wells had results below the lab's detection limit, so the median is reported as below that limit.
Hardness Recent
| Level it's compared with | none; hardness is shown in bands |
|---|---|
| Share of wells very hard | 63% |
| Median | 254 mg/L as CaCO₃ |
| Years sampled | 1923–2024 |
| Wells | 2,275 |
| Test results | 8,869 |
| Wells left out | 190 |
| Sources | USGS (1,944), AZDEQ_GW (208), 21ARIZGW (120), FMYN_WQX (2), SRPMIC_WQX (1) |
Sulfate Recent
| Level it's compared with | 250 mg/L |
|---|---|
| Share of wells over the level | 25% |
| Wells over the level / wells judged | 542 of 2151 |
| Median | 120 mg/L |
| Years sampled | 1920–2024 |
| Wells | 2,151 |
| Test results | 8,303 |
| Wells left out | 279 |
| Sources | USGS (1,933), AZDEQ_GW (213), SRPMIC_WQX (3), FMYN_WQX (2) |