Why Dwid, AZ
Exceeded the action level in the past
Latest 90th-percentile lead: reported as 0 (not detected) (monitoring period 2026-2026). The federal action level is 15 ppb today and drops to 10 ppb in Nov 2027; EPA's health goal is 0. The latest result is under the action level, but this system has gone over 15 ppb before. Lead comes from pipes, not the source water, so a home with a lead service line can still be exposed. Test your own tap.
About Why Dwid
Why Dwid serves about 400 people through 118 service connections, which makes it a very small system under EPA's size classes. It is privately owned and draws groundwater, in Pima County, Arizona. EPA system ID: AZ0410118; phone on file: 520-387-5460. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Lead results over time
Against the period ending 2025 (0 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Why Dwid is 23 ppb across 13 monitoring periods, 2 of them over the 15 ppb action level.
| Period ending | 90th-percentile lead |
|---|---|
| 2026 | 0 (not detected) |
| 2025 | 0 (not detected) |
| 2024 | 1.8 ppb |
| 2023 | 0 (not detected) |
| 2023 | 0 (not detected) |
| 2022 | 2.3 ppb |
| 2022 | 23 ppb over 15 |
| 2021 | 0 (not detected) |
| 2021 | 0 (not detected) |
| 2020 | 23 ppb over 15 |
| 2019 | 0 (not detected) |
| 2017 | 0 (not detected) |
| 2016 | 3.3 ppb |
How Why Dwid compares
Of the 730 Arizona systems with a lead result, the median latest reading is 0 ppb; 9 are over 15 ppb right now and 58 have gone over at some point. Why Dwid's reported as 0 (not detected) sits at the 32nd percentile in Arizona and the 21st nationally (higher means more lead). Systems reporting 0 tie at the bottom, so the rank mostly reflects size among them.
Neighbouring systems
137 other systems share Pima County; 44 of them have a higher latest lead result than Why Dwid. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Tucson City Of | 732,906 | 0.65 ppb |
| Metropolitan Dwid | 45,570 | 0.57 ppb |
| Oro Valley Water Utility | 42,316 | 1 ppb |
| Community Wc Of Green Valley | 22,085 | 0 (not detected) |
| Usaf Davis Monthan Afb | 18,640 | 0 (not detected) |
| Sahuarita Water Company | 18,178 | 0 (not detected) |
| Vail Water Company | 17,500 | 0 (not detected) |
| Flowing Wells Irrigation District | 16,000 | 0 (not detected) |
| Marana Municipal - Marana | 15,162 | 0 (not detected) |
| Tucson Water Corona De Tucson | 10,217 | 0.78 ppb |
Your move
Test your own tap with a certified lab first-draw sample; Ajo, AZ may offer free or low-cost kits through the utility. If your own line is lead, replacing the private side runs about $1,200-$12,300 (EPA average about $4,700). Ask Why Dwid whether it covers that cost before hiring anyone - many utilities now do. Its latest copper 90th percentile is 5860 ppb (copper action level 1,300 ppb).
These figures describe homes the utility sampled, not your tap. Only your service line record or a test of your own water answers the question for your house. What a 90th-percentile result does and does not tell you: how to read a lead result. Why an old exceedance still matters: over the limit before, under it now.