Is Durham, CA tap water safe?
The short answer
1 of the 6 utilities serving Durham has a result above a legal limit or action level, or a health-based violation since 2016, in EPA’s and California’s records: Thermalito Water & Sewer Dist.
Cal - Water Service Co. - Chico, which serves the most people here, has 3 results above EPA’s new limit, which takes effect in 2029 and 2 results above the health goal. The worst: PFOS at 22.5 ppt, above EPA’s new limit, which takes effect in 2029.
The water from Cal - Water Service Co. - Chico is moderately hard to very hard depending on the source, 84 to 295 mg/L (4.9 to 17.3 grains per gallon). How California’s water compares.
A town can be served by more than one utility, and some homes are on private wells. The name on your water bill tells you which is yours, and your ZIP code narrows it down. They are listed by how many people each serves in Durham’s ZIP codes, from EPA’s estimates.
- Open report
Cal - Water Service Co. - Chico
California · serves 110,473 people · about 6,600 in Durham
3 results above EPA’s new limit, which takes effect in 2029 and 2 results above the health goal. The worst: PFOS at 22.5 ppt, above EPA’s new limit, which takes effect in 2029. Hardness: moderately hard to very hard depending on the source, 84 to 295 mg/L (4.9 to 17.3 grains per gallon).
No health-based violations since 2016
- Open report
Durham Irrigation District
California · serves 1,581 people · about 1,100 in Durham
1 result above the health goal. The worst: Lead at 0.74 ppb, above the health goal.
No health-based violations since 2016
- Open report
Thermalito Water & Sewer Dist
California · serves 12,209 people · about 360 in Durham
1 result above the legal limit, 1 result above EPA’s new limit, which takes effect in 2029, 1 result above the health goal and 1 result above EPA’s health benchmark. The worst: Haloacetic acids (HAA5) at 47.5 ppb, above the legal limit. Hardness: soft to moderately hard depending on the source, 36 to 117 mg/L (2.1 to 6.8 grains per gallon).
1 health-based violation since 2016
- Open report
Cal - Water Service Co. - Oroville
California · serves 11,047 people · about 140 in Durham
2 results above the health goal and 1 result above EPA’s health benchmark. The worst: Lithium at 81.3 ppb, above EPA’s health benchmark. Hardness: soft to hard depending on the source, 37 to 145 mg/L (2.2 to 8.5 grains per gallon).
No health-based violations since 2016
- Open report
Butte Creek Estates Mutual Water Co
California · serves 399 people · under 100 in Durham
Nothing in its records is above a health goal. Hardness: moderately hard, typically 79 mg/L (4.6 grains per gallon).
No health-based violations since 2016
- Open report
Gran Mutual Water Co
California · serves 290 people · under 100 in Durham
Nothing in its records is above a health goal. Hardness: moderately hard, typically 109 mg/L (6.4 grains per gallon).
No health-based violations since 2016
What handles it
Each of these is certified, on a certifier’s listing, for a result above a line in Cal - Water Service Co. - Chico’s water, which serves the most people here. Another utility’s report names what handles its own results.
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Countertop reverse osmosis
- IAPMO listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 4, 2026
Certified for: PFOS, PFOA, Arsenic
Aquasana SmartFlow Reverse Osmosis (AQ-SFRO2)
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: PFOS, PFOA, Arsenic
Brondell Capella RC250 Reverse Osmosis System
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: PFOS, PFOA, Arsenic
Water testing near Durham
The 3 labs California certifies closest to Durham, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Fruit Growers Laboratory, Inc.
Chico, CA · about 10 miles
Certified for bacteria
Cranmer Engineering, Inc.
Grass Valley, CA · about 46 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics
Eurofins Sacramento Service Center
West Sacramento, CA · about 72 miles
Certified for bacteria, nitrate, minerals and other inorganics
Which ZIP codes are in Durham: Census 2020 relationship files. Which utilities serve them, and how many people: EPA SDWIS and EPA’s service area map. Each utility’s results: EPA UCMR 5, EPA SDWIS, and EPA’s and the state’s compliance monitoring, as its report lists them. How they are measured: methodology. Certified labs: California State Water Resources Control Board, ELAP accredited laboratories and their fields of accreditation; distances from the Census 2020 ZIP code tabulation area gazetteer.
Near Durham
Towns nearby with a page of their own.
What to do next
- Read Cal - Water Service Co. - Chico’s full reportEvery result with its dates, the violations, and the certification claim that handles each finding.Open the report
- Filters for PFOSRanked by certification and what they cost over five years.The best water filters for PFAS, ranked
- On a private well?No utility tests a well. A certified lab test is the first step.How to test well water