Tonto Hills Dwid, AZ
Exceeded the action level in the past
Latest 90th-percentile lead: reported as 0 (not detected) (monitoring period 2025-2025). 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 Tonto Hills Dwid
Tonto Hills Dwid serves about 350 people through 150 service connections, which makes it a very small system under EPA's size classes. It is privately owned and draws surface water, in Maricopa County, Arizona. EPA system ID: AZ0407076; phone on file: 480-595-0128. Ask them for your address in their service line inventory - every system had to publish one by Oct 2024.
Every lead result on file
Against the period ending 2024 (0 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Tonto Hills Dwid is 16 ppb across 9 monitoring periods, 2 of them over the 15 ppb action level.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 0 (not detected) |
| 2024 | 0 (not detected) |
| 2024 | 16 ppb over 15 |
| 2023 | 0 (not detected) |
| 2022 | 16 ppb over 15 |
| 2021 | 0 (not detected) |
| 2019 | 0 (not detected) |
| 2018 | 1.9 ppb |
| 2016 | 1.9 ppb |
Against other Arizona systems
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. Tonto Hills Dwid's reported as 0 (not detected) sits at the 30th percentile in Arizona and the 20th nationally (higher means more lead). Systems reporting 0 tie at the bottom, so the rank mostly reflects size among them.
Nearby utilities
99 other systems share Maricopa County; 24 of them have a higher latest lead result than Tonto Hills Dwid. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Phoenix City Of | 1,695,000 | 2.74 ppb |
| Mesa City Of | 466,000 | 5.01 ppb |
| Gilbert, Town Of | 247,600 | 0 (not detected) |
| Chandler City Of | 247,328 | 1.4 ppb |
| Scottsdale City Of | 241,361 | 2.3 ppb |
| Glendale City Of | 234,766 | 2.11 ppb |
| Peoria City Of | 187,676 | 0 (not detected) |
| Tempe City Of | 165,000 | 4.4 ppb |
| Epcor - Agua Fria | 128,040 | 0 (not detected) |
| Avondale City Of | 96,130 | 0 (not detected) |
Your move
Test your own tap with a certified lab first-draw sample; Cave Creek, 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 Tonto Hills Dwid whether it covers that cost before hiring anyone - many utilities now do.
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. More in what a past exceedance means today.