Pima County, AZ
These figures come from wells tested in Pima County, AZ, not from any one well.
- Iron, manganese and sulfate are not common in wells in Pima County, AZ (5 of 145, 11 of 146 and 63 of 1119 tested wells were over). Only a test tells you about your own well.
- Wells in Pima County, AZ are typically hard (1214 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:
- iron
- manganese
- hardness
- sulfate
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 | 3.4% |
| Wells over the level / wells judged | 5 of 145 |
| Median | < 14 mg/L |
| Years sampled | 1917–2024 |
| Wells | 145 |
| Test results | 1,372 |
| Wells left out | 29 |
| Sources | USGS (683), 21ARIZGW (100), AZDEQ_GW (96), 11NPSWRD_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 | 7.5% |
| Wells over the level / wells judged | 11 of 146 |
| Median | < 0.05 mg/L |
| Years sampled | 1971–2024 |
| Wells | 146 |
| Test results | 1,147 |
| Wells left out | 56 |
| Sources | USGS (542), 21ARIZGW (100), AZDEQ_GW (96), 11NPSWRD_WQX (1), 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.
Hardness Recent
| Level it's compared with | none; hardness is shown in bands |
|---|---|
| Share of wells very hard | 36% |
| Median | 130 mg/L as CaCO₃ |
| Years sampled | 1917–2024 |
| Wells | 1,214 |
| Test results | 2,076 |
| Wells left out | 65 |
| Sources | USGS (1,023), 21ARIZGW (95), AZDEQ_GW (95), 11NPSWRD_WQX (1) |
Sulfate Recent
| Level it's compared with | 250 mg/L |
|---|---|
| Share of wells over the level | 5.6% |
| Wells over the level / wells judged | 63 of 1119 |
| Median | 35 mg/L |
| Years sampled | 1917–2024 |
| Wells | 1,119 |
| Test results | 1,830 |
| Wells left out | 113 |
| Sources | USGS (1,025), AZDEQ_GW (94) |