Gswc - Norwalk, CA
Lead reported as not detected
Latest 90th-percentile lead: reported as 0 (not detected) (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. The latest 90th-percentile result was reported as 0 (not detected at the lab's limit). That says the sampled homes were low, not that your home has no lead service line. Check your utility's service line inventory for your address.
Who runs the water here
Gswc - Norwalk serves about 43,167 people through 9,416 service connections, which makes it a large system under EPA's size classes. It is privately owned and draws surface water, in Los Angeles County, California. EPA system ID: CA1910098; phone on file: 626-250-1517. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Every lead result on file
Against the period ending 2022 (0 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Gswc - Norwalk is 0 ppb across 4 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 0 (not detected) |
| 2022 | 0 (not detected) |
| 2019 | 0 (not detected) |
| 2016 | 0 (not detected) |
Where this result ranks
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. Gswc - Norwalk's reported as 0 (not detected) sits at the 58th percentile in California and the 40th nationally (higher means more lead). Systems reporting 0 tie at the bottom, so the rank mostly reflects size among them.
Other water systems in Los Angeles County
197 other systems share Los Angeles County; 42 of them have a higher latest lead result than Gswc - Norwalk. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Los Angeles-City, Dept. Of Water & Power | 3,875,566 | 3.9 ppb |
| Long Beach Utilities Department | 466,772 | 0.97 ppb |
| Santa Clarita Valley Water Agency | 292,014 | 0 (not detected) |
| Gswc - Southwest | 277,740 | 1.7 ppb |
| San Gabriel Valley Water Co.-El Monte | 240,000 | 0 (not detected) |
| Los Angeles Cwwd 40 Reg 4 & 34 Lancaster | 208,129 | 1.8 ppb |
| Glendale-City, Water Dept. | 192,212 | 5.3 ppb |
| Suburban Water Systems-San Jose | 170,523 | 0 (not detected) |
| Pasadena Water And Power | 165,448 | 1.9 ppb |
| Pomona - City, Water Dept. | 151,713 | 2.1 ppb |
What to do in your house
Look up your address in Gswc - Norwalk's service line inventory. If it says lead, galvanized or unknown, test your tap. If your own line is lead, replacing the private side runs about $1,200-$12,300 (EPA average about $4,700). Ask Gswc - Norwalk 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. Why sampled homes are the worst-case ones is in the guide to reading the number. Small systems behave differently: why small systems go over more often.