Los Angeles County, CA · PWSID CA1910142
Gswc-San Dimas lead service lines
No lead lines reported
Gswc-San Dimas reported 16,303 service lines and no lead, galvanized-requiring-replacement or unknown lines. That's good news for the service line. Older homes can still have lead solder or brass fixtures inside, so testing is the only sure check.
0% of Gswc-San Dimas's service lines are lead or galvanized requiring replacement. That's lower than the California average (0.1%) and lower than the national average (3.1%).
- Lead 0%
- Galvanized (replace) 0%
- Unknown 0%
- Non-lead 100%
Total service lines reported: 16,303. Reported all required service line types. Population served: 56,564; 16,184 connections.
Lead test results
Gswc-San Dimas's most recent 90th-percentile lead result (Jan 2026–Jun 2026) was 1.2 ppb, below both the 15 ppb action level and the 10 ppb level that takes effect in 2027. This means 90% of homes sampled were at or below that level; individual homes, especially those with lead lines, can be higher.
Lead and Copper Rule 90th-percentile results reported to EPA, in parts per billion. Dashed lines: 15 ppb action level and the 10 ppb level from November 1, 2027.
Lead rule violations
EPA's data lists no Lead and Copper Rule violations for Gswc-San Dimas since 2015. That covers testing, reporting, corrosion control and public notice requirements; it isn't a guarantee about any individual home.
Source: EPA SDWIS violation records for the Lead and Copper Rule.
Where the water comes from
Gswc-San Dimas's main water source is purchased surface water. It buys treated water from Covina Valley Water Company - Wholesale, Three Valleys MWD, Walnut Valley Water District. The seller treats the water, including corrosion control that keeps lead from dissolving out of pipes, while Gswc-San Dimas is responsible for its own service line inventory and replacement program.
Source: EPA SDWIS water system and facility records.
Check your own address
These counts cover the whole system. To see whether your line is lead, use the utility's address-level inventory. Utilities had to prepare one by October 16, 2024 and make it publicly accessible; systems serving more than 50,000 people must post it online.
No map yet? Do the 2-minute scratch and magnet test on the pipe where water enters your home.
Protect your drinking water now
If your line is lead, galvanized or unknown, filter water for drinking, cooking and baby formula. Use a filter certified to NSF/ANSI 53 for lead. Run cold water for a few minutes after it sits for hours, and never use hot tap water for cooking.
How to pick a lead-certified filter · How to test your water for lead
Getting the line replaced
EPA's Lead and Copper Rule Improvements require most systems to replace lead and galvanized-requiring-replacement lines by December 31, 2037. Ask Gswc-San Dimas whether it replaces the private side for free or with a cost share before you hire anyone. If you want it done sooner, or your utility doesn't cover your side, a licensed plumber can quote it. What replacement costs.
County pages: Lead pipes in Los Angeles County
Cities served
ZIP codes served
ZIP codes whose center falls inside Gswc-San Dimas's mapped service area (EPA service area boundaries). Neighboring utilities may serve parts of the same ZIP.
91773
Other water systems nearby
Check another water system
Questions
Does Gswc-San Dimas have lead pipes?
Gswc-San Dimas reported no lead, galvanized-requiring-replacement or unknown service lines among 16,303 lines.
How do I check if my home's service line is lead?
Look up your address on Gswc-San Dimas's official service line inventory, which utilities must make publicly available. You can also scratch the pipe where it enters your home: lead is soft, dull gray, scratches to shiny silver and does not attract a magnet.
When will Gswc-San Dimas replace lead service lines?
Under EPA's Lead and Copper Rule Improvements, most systems must replace lead and galvanized-requiring-replacement lines by December 31, 2037, starting from November 1, 2027. The rule is being challenged in court, so dates could change. Many utilities run free or cost-share programs now.
Has Gswc-San Dimas had lead violations?
EPA's data shows no Lead and Copper Rule violations since 2015 for Gswc-San Dimas.
Which water filters remove lead?
Use a filter certified to NSF/ANSI Standard 53 for lead reduction, or NSF/ANSI 58 for reverse osmosis. Check the certification on NSF's listings, not just the box.
Embed or cite this data
Local news sites, blogs and community groups can embed this card. It updates when EPA releases new data.
Citation: Lead Pipe Map, "Gswc-San Dimas lead service lines," https://leadpipemap.com/ca/gswc-san-dimas/. Source: EPA SDWIS service line inventory, 2026 Q3. Download the full dataset on the data page.