Gswc - Southwest water quality report, rewritten
- Serves
- 277,740
- Connections
- 52,644
- Water source
- Surface water bought from another system
- Based in
- Hawthorne, CA
- County
- Los Angeles
- Owner
- Private
The 21 ZIP codes it serves
90017, 90030, 90044, 90045, 90047, 90059, 90061, 90220, 90222, 90245, 90247, 90248, 90249, 90250, 90260, 90278, 90301, 90303, 90304, 90745, 90746
PWSID CA1910155 · EPA data
Read this first
- Lithium (above EPA’s health benchmark) was found in four of 18 samples, highest 51.3 ppb. Above EPA’s health reference level of 10 ppb, a screening level rather than an enforceable limit.
No health-based violations on file since 2016.
What was found
Highlighted: above the health goal, or EPA’s health benchmark where there is no goal. Circled: above the legal limit in at least one sample, or the action level. Every scale puts that line at its middle.
PFAS and lithium: EPA UCMR 5, samples taken from June 18, 2024 to March 10, 2025. Each blue tick on a scale is one sample where it was found.
Lithium (above EPA’s health benchmark)
Comes from the source
51.3ppb
Highest of 18 samples; found in four
Above EPA’s health reference level of 10 ppb, a screening level rather than an enforceable limit.
What handles it
No certification claim covers this compound yet.
Tested and not found
Below EPA’s minimum reporting level in every sample taken from June 18, 2024 to March 10, 2025. Not found means not measured above that level, which is not the same as zero.
All 30 compounds tested and not found
- 11Cl-PF3OUdS
- 4:2 FTS
- 6:2 FTS
- 8:2 FTS
- 9Cl-PF3ONS
- ADONA
- HFPO-DA (GenX)
- Lead
- NEtFOSAA
- NFDHA
- NMeFOSAA
- PFBA
- PFBS
- PFDA
- PFDoA
- PFEESA
- PFHpA
- PFHpS
- PFHxA
- PFHxS
- PFMBA
- PFMPA
- PFNA
- PFOA
- PFOS
- PFPeA
- PFPeS
- PFTA
- PFTrDA
- PFUnA
Violations since 2016
No health-based violations on file with EPA since 2016.
What this report cannot tell you
- Levels of everything else. Federal bulk data carries results for PFAS, lithium, lead and copper, and violations for the rest. Nitrate, arsenic, disinfection byproducts and other levels are in Gswc - Southwest’s own annual report, which it must send you every year.
- Your own plumbing. Lead results are the 90th percentile across homes the utility samples. Your home’s service line, solder and fixtures decide yours. A certified lab test is the only way to know.
- Anything after the latest data. SDWIS data is from 2026 Q2; UCMR 5 samples are from June 18, 2024 to March 10, 2025.
Other California utilities
- Los Angeles - City, Dept. of Water & Power3.9 million
- East Bay MUD1.4 million
- City of San Diego1.4 million
- San Jose Water1 million
- SFPUC City Distribution Division848,019
- Eastern Municipal WD666,581
- City of Fresno545,716
- City of Sacramento Main527,979
- Long Beach Utilities Department466,772
- Irvine Ranch Water District444,800
- City of Anaheim348,593
- Alameda County Water District344,000
Sources
- EPA UCMR 5 occurrence data, file of Aug. 27, 2026
- EPA SDWA bulk download (SDWIS federal data), 2026 Q2
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
What to do next
Read up on Lithium
What each one does to health, where it comes from, and the certification claim that addresses it.
About LithiumGet the utility’s own report
Gswc - Southwest must send you a water quality report every year. It lists nitrate, arsenic and byproduct levels this page cannot.
How to read itTest your own tap for lead
Your service line, solder and fixtures decide the lead at your faucet, not the utility’s average.
Lead in your water: what to doDecide if you want a filter at all
A filter for taste or chlorine is a preference, not a need. The standards say what each kind can do.
NSF/ANSI standards, decoded