Well Water Testing Requirements in California (CA)
California does not mandate ongoing private well testing but strongly recommends annual testing. New wells require bacteria and nitrate testing. Some counties have stricter local requirements. The state has ~800,000 private wells, many in agricultural areas with nitrate contamination risk. The state has approximately 800,000 private wells.
Required Contaminant Tests in California
California requires testing for the following 2 contaminants for new wells:
Common Contaminants in California Well Water
Based on geological conditions, land use patterns, and historical testing data, these contaminants are commonly found in California private wells. Even if not required by law, testing for these contaminants is recommended.
Testing Requirements by City in California
Local testing requirements may vary from state-level regulations. Some counties and municipalities have stricter rules than the state minimum. Below are details for major cities in California.
| City | Testing Required | Notes |
|---|---|---|
| Fresno | No | San Joaquin Valley; nitrate and 1,2,3-TCP concerns |
| Sacramento | No | State capital; many private wells in surrounding areas |
| San Diego | No | County recommends annual testing |
| Bakersfield | No | Agricultural area; nitrate and arsenic concerns |
| Modesto | No | Central Valley; DBCP contamination history |
Testing Recommendations for California Well Owners
- Even though your state does not require testing, the EPA recommends testing private well water annually for bacteria and nitrate.
- Arsenic is a known contaminant in your state. Test for arsenic at least once, even if not required.
- Nitrate contamination is common in your area. Test annually, especially if near agricultural land.
Understanding California's Well Water Regulations
Testing Frequency
California does not require ongoing testing of private well water. However, the EPA recommends all private well owners test annually for bacteria and nitrate, regardless of state requirements. Proactive testing is the only way to ensure your well water is safe.
New Well Requirements
California requires testing when a new well is constructed or an existing well is significantly modified. The required tests include bacteria (coliform/e. coli), nitrate, and the well must pass these tests before being put into service for drinking water. Well construction must comply with state standards and a permit is required before drilling.
State Laboratory and Testing Resources
California operates a state laboratory or participates in a state lab network that provides water testing services, often at subsidized rates below commercial laboratory prices. Contact your state health department or environmental agency for current pricing and sample submission procedures. Many county health departments also offer basic bacteria testing, sometimes at no cost. The average cost for a comprehensive well water test in California is approximately $250, though a basic bacteria and nitrate screen may cost significantly less.
How California Compares
California has a minimal level of well water testing regulation. Below are other states with similar regulatory approaches.
| State | Testing Required | Test at Sale | Required Tests | Avg. Cost |
|---|---|---|---|---|
| California (CA) | No | No | 2 | $250 |
| Alabama (AL) | No | No | 1 | $150 |
| Alaska (AK) | No | No | 2 | $200 |
| Arizona (AZ) | No | No | 2 | $175 |
| Arkansas (AR) | No | No | 1 | $125 |
| Colorado (CO) | No | No | 1 | $175 |
Check Other States
Use our well water testing lookup tool to check requirements for any state, or browse all 50 states ranked by testing strictness. If you are moving to or buying property in California, understanding the testing requirements is an important part of your due diligence.