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Tap water quality report

Gswc - Norwalk

EPA monitoring tested this supplier for 106 contaminants and detected 32. A detection doesn't automatically mean the water is unsafe — the level and EPA source for each is below.

106
contaminants tested
32
detected
43,167
people served
0
health-based violations
California rankingsLead in CaliforniaPFAS in California
Water source
SWP
Ownership
Private
Counties served
Los Angeles

Compliance record

Formal violations the EPA has on file for this supplier. A health-based violation means a contaminant limit or a required treatment was breached; the rest are monitoring or reporting failures — still violations, but not a measured health risk.

0
health-based violations
1
violations on file
0
still open
ViolationTypeStatusPeriod
Other Monitoring Archived 1988-09-01 → 1988-09-30

PFAS detected

PFAS are industrial “forever chemicals”. These are the EPA's latest nationwide test results (2023–2025).
ContaminantMaxDetection ratePeriod
Pfba 0.0073 µg/L 4/14 2025
Pfhxa 0.0130 µg/L 2/14 2025
Pfpea 0.0150 µg/L 2/14 2025

Other contaminants detected

Each bar shows the measured level as a share of the EPA limit: green is well under, amber is close to it, red is over. For lead and copper the limit applies to exactly the 90th-percentile figure shown, so red there means a real exceedance. For everything else the limit applies to a running annual average while the figure is the single worst sample on record — over 100% is worth reading, but is not by itself a violation. Formal violations are listed separately.
ContaminantLevel vs EPA limitDetection rateSourcePeriod
1,1-Dichloroethylene
36 µg/L 514%
of the EPA limit, in the worst sample — 7 µg/L
 1042/2473 SYR4 2012–2019
1,2-Dichloroethane
2.3 µg/L 46%
of the EPA limit 5 µg/L
 613/1849 SYR4 2012–2019
Trichloroethylene
64 µg/L 1280%
of the EPA limit, in the worst sample — 5 µg/L
 429/2444 SYR4 2012–2019
Tetrachloroethylene
88 µg/L 1760%
of the EPA limit, in the worst sample — 5 µg/L
 350/2445 SYR4 2012–2019
Nitrate
8814 µg/L 88%
of the EPA limit 10000 µg/L
 306/312 SYR4 2012–2019
cis-1,2-Dichloroethylene
8.9 µg/L 13%
of the EPA limit 70 µg/L
 240/589 SYR4 2012–2019
TTHM
70 µg/L 88%
of the EPA limit 80 µg/L
 115/149 SYR4 2012–2019
Dibromoacetic Acid
6.5 µg/L
No EPA limit set
 112/124 SYR4 2012–2019
Total Haloacetic Acids (HAA5)
30 µg/L 50%
of the EPA limit 60 µg/L
 112/124 SYR4 2012–2019
Bromoform
24 µg/L
No EPA limit set
 111/148 SYR4 2012–2019
Bromodichloromethane
22 µg/L
No EPA limit set
 109/148 SYR4 2012–2019
Dibromochloromethane
24 µg/L
No EPA limit set
 109/148 SYR4 2012–2019
Chloroform
37 µg/L
No EPA limit set
 102/148 SYR4 2012–2019
Dichloroacetic Acid
15 µg/L
No EPA limit set
 94/124 SYR4 2012–2019
Trichloroacetic Acid
8.7 µg/L
No EPA limit set
 70/124 SYR4 2012–2019
Fluoride
590 µg/L 15%
of the EPA limit 4000 µg/L
 51/51 SYR4 2012–2019
Lead
0.0 mg/L 0%
of the EPA limit 0.0150 mg/L
 34/34 LCR 2025
Monobromoacetic Acid
2.4 µg/L
No EPA limit set
 26/124 SYR4 2012–2019
Monochloroacetic Acid
6.2 µg/L
No EPA limit set
 26/124 SYR4 2012–2019
1,2-Dichloropropane
0.8300 µg/L 17%
of the EPA limit 5 µg/L
 14/206 SYR4 2012–2019
Selenium
15 µg/L 30%
of the EPA limit 50 µg/L
 13/21 SYR4 2012–2018
Arsenic
4.5 µg/L 45%
of the EPA limit 10 µg/L
 11/23 SYR4 2012–2018
Barium
170 µg/L 8.5%
of the EPA limit 2000 µg/L
 10/21 SYR4 2012–2018
Combined Uranium
9.983 µg/L 33%
of the EPA limit 30 µg/L
 9/13 SYR4 2013–2019
Nitrate-Nitrite
8300 µg/L 83%
of the EPA limit 10000 µg/L
 6/8 SYR4 2015–2018
Copper
9 µg/L 0.7%
of the EPA limit 1300 µg/L
 5/21 SYR4 2012–2018
Lithium
58 µg/L
No EPA limit set
 4/14 UCMR-5 2025
Chromium
6.5 µg/L 6.5%
of the EPA limit 100 µg/L
 3/21 SYR4 2012–2018
Mercury
0.2100 µg/L 11%
of the EPA limit 2 µg/L
 1/21 SYR4 2012–2018
74 contaminants tested, none detected
1,1,1-Trichloroethane1,1,2-Trichloroethane1,2,4-Trichlorobenzene1,2-DIBROMO-3-CHLOROPROPANE11Cl-PF3OUdS2,3,7,8-TCDD2,4,5-TP2,4-D4:2 Fts6:2 Fts8:2 Fts9Cl-PF3ONSAdonaAntimony, TotalBhc-GammaBenzeneBeryllium, TotalChlorobenzeneCyanideCadmiumCarbofuranCarbon TetrachlorideChlordaneCombined Radium (-226 And -228)DichloromethaneDalaponDi(2-ethylhexyl) PhthalateDinosebDiquatEthylene DibromideEndothallEndrinEthylbenzeneGlyphosateGross Beta Particle ActivityHfpo-DaHeptachlorHeptachlor EpoxideLassoLeadMethoxychlorNetfosaaNfdhaNmefosaaNitriteOxamylPFBSPfdaPfdoaPfeesaPfhpaPfhpsPFHXSPfmbaPfmpaPFNAPFOAPFOSPfpesPftaPftrdaPfunaPentachlorophenolPicloramStyreneThallium, TotalTolueneTotal Polychlorinated Biphenyls (PCB)ToxapheneVinyl ChlorideXylenes, TotalO-DichlorobenzeneP-Dichlorobenzenetrans-1,2-Dichloroethylene

Utility contact

Contact
FLORES, ROCIO
Phone
626-250-1517
Email
Rocio.Flores@gswater.com

Frequently asked questions about Gswc - Norwalk

Is Gswc - Norwalk tap water safe to drink?

EPA monitoring detected 32 contaminants in Gswc - Norwalk's water. A detection isn't the same as a violation — most levels are within federal limits. See each level and source above, and the utility's annual Consumer Confidence Report for its official compliance status.

What contaminants were detected in Gswc - Norwalk's water?

EPA monitoring detected 1,1-Dichloroethylene, 1,2-Dichloroethane, Trichloroethylene, Tetrachloroethylene, Nitrate, and others. The full list with the level and data source for each is above.

How many people does Gswc - Norwalk serve?

Gswc - Norwalk reports serving 43,167 people in California, per its EPA record.

Has Gswc - Norwalk had any water quality violations?

The EPA has 1 violation on file for Gswc - Norwalk, of which 0 are health-based (a contaminant limit or required treatment was breached) and 0 remain open. The rest are monitoring or reporting failures.

Where does this data come from?

Every figure is official EPA drinking-water monitoring — the Lead & Copper Rule, the UCMR-5 nationwide testing program, and the EPA Six-Year Review — not our own testing. Each number is labelled with its source and period.