Cwsc Los Altos Suburban, CA
Lead detected, under the action levels
Latest 90th-percentile lead: 1.5 ppb (monitoring period 2023-2025). The federal action level is 15 ppb today and drops to 10 ppb in Nov 2027; EPA's health goal is 0. Lead was measured in sampled homes but the 90th percentile is under both action levels. EPA's health goal for lead is zero, so test your own tap if your home was built before 1986 or anyone in it is pregnant or a young child.
Who runs the water here
Cwsc Los Altos Suburban serves about 63,559 people through 18,530 service connections, which makes it a large system under EPA's size classes. It is privately owned and draws surface water, in Santa Clara County, California. EPA system ID: CA4310001; phone on file: 408-367-8593. Ask them for your address in their service line inventory - every system had to publish one by Oct 2024.
Lead results over time
Against the period ending 2022 (2.5 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Cwsc Los Altos Suburban is 2.5 ppb across 4 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 1.5 ppb |
| 2022 | 2.5 ppb |
| 2019 | 0 (not detected) |
| 2018 | 0 (not detected) |
How Cwsc Los Altos Suburban compares
Of the 2,884 California systems with a lead result, the median latest reading is 0 ppb; 30 are over 15 ppb right now and 215 have gone over at some point. Cwsc Los Altos Suburban's 1.5 ppb sits at the 75th percentile in California and the 64th nationally (higher means more lead).
Other water systems in Santa Clara County
72 other systems share Santa Clara County; 19 of them have a higher latest lead result than Cwsc Los Altos Suburban. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| San Jose Water | 1,039,920 | 0 (not detected) |
| City Of Sunnyvale | 157,566 | 0 (not detected) |
| City Of Santa Clara | 134,587 | 2.7 ppb |
| Great Oaks Wc Inc | 112,582 | 0 (not detected) |
| City Of San Jose - Evg/Edv/Coy | 99,783 | 0 (not detected) |
| City Of Milpitas | 81,915 | 2.5 ppb |
| City Of Mountain View | 81,340 | 0 (not detected) |
| City Of Palo Alto | 67,658 | 0 (not detected) |
| City Of Gilroy | 59,426 | 2 ppb |
| City Of San Jose - Nsj/Alviso | 48,082 | 0 (not detected) |
What to do in your house
Test your own tap with a certified lab first-draw sample; San Jose, CA 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 Cwsc Los Altos Suburban 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. The lead result guide covers how utilities pick the homes they sample. Systems that went over once often dip back under; here is what that means.