Whatcom County, WA · PWSID WA5319200
Diablo WTR Sys-Seattle City Light lead service lines
2 lines still unidentified
Diablo WTR Sys-Seattle City Light reported no confirmed lead service lines, but 2 of 25 lines (8.0%) are still listed as "lead status unknown." Until a line is identified, treat it as possibly lead.
0% of Diablo WTR Sys-Seattle City Light's service lines are lead or galvanized requiring replacement. That's lower than the Washington average (0.3%) and lower than the national average (3.1%).
- Lead 0%
- Galvanized (replace) 0%
- Unknown 8.0%
- Non-lead 92%
Total service lines reported: 25. Reported all required service line types. Population served: 53; 41 connections.
Lead test results
Diablo WTR Sys-Seattle City Light's most recent 90th-percentile lead result (Jan 2022–Dec 2024) was 15.5 ppb, above the 15 ppb federal action level. 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.
Progress since 2025 Q1
Reported lead and galvanized-requiring-replacement lines went from 0 in 2025 Q1 to 0 in 2026 Q3: no change. Lines of unknown material went from 2 to 2, no change.
Quarterly counts reported to EPA. A drop usually means lines were replaced or confirmed non-lead; a rise usually means more lines were identified. Replacement progress rankings.
Lead rule violations
EPA's data lists 1 Lead and Copper Rule violation since 2015, 1 health-based for Diablo WTR Sys-Seattle City Light. Health-based violations are treatment failures, such as corrosion control or public education; the rest are missed monitoring or reporting.
| Began | Violation | Status |
|---|---|---|
| Oct 2025 | Corrosion control study or recommendation not done health-based | Returned to compliance |
Source: EPA SDWIS violation records for the Lead and Copper Rule.
Where the water comes from
Diablo WTR Sys-Seattle City Light's main water source is groundwater (wells).
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 Diablo WTR Sys-Seattle City Light 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 Whatcom County
Other water systems nearby
| System | Lead + galv. | Unknown |
|---|---|---|
| City of Blaine | 0 | 1,729 |
| Sandy Point Improvement Co | 0 | 386 |
| Deer Creek Water Assoc. | 0 | 613 |
| Whatcom County Water Dist 13 | 0 | 423 |
| Delta Water Association | 0 | 181 |
| Newhalem Water System | 15 | 0 |
| Everson Water Assoc | 3 | 0 |
| Century Water Association | 30 | 0 |
Check another water system
Questions
Does Diablo WTR Sys-Seattle City Light have lead pipes?
It hasn't confirmed any, but 2 of its 25 service lines are still of unknown material, so lead has not been ruled out.
How do I check if my home's service line is lead?
Look up your address on Diablo WTR Sys-Seattle City Light'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 Diablo WTR Sys-Seattle City Light 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 Diablo WTR Sys-Seattle City Light had lead violations?
EPA's data shows 1 Lead and Copper Rule violation since 2015, 1 health-based for Diablo WTR Sys-Seattle City Light.
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, "Diablo WTR Sys-Seattle City Light lead service lines," https://leadpipemap.com/wa/diablo-wtr-sys-seattle-city-light/. Source: EPA SDWIS service line inventory, 2026 Q3. Download the full dataset on the data page.