Well Water Water Testing

Disclaimer: The Sonoma County Department of Health Services makes no assumption of quality and makes no warranties regarding providers appearing in this resource guide. This resource guide is simply a public listing provided for consumer convenience and is not a recommendation or endorsement by the Department.

Water Quality Tests

There are many tests that can be performed on your well water to determine its water quality. This is a list of the most commonly performed tests and their recommended testing frequencies. Because bacteria and nitrate are the most common contaminants of well water, they should be tested more frequently. The minerals test is recommended for the purposes of developing a baseline understanding of your water and as a way to indicate water quality changes.

Bacteria

• Test type: EPA Colilert Method, Total Coliform and Fecal Coliform
• Frequency: twice a year or after a flood or other disaster that may have impacted the well
• If the lab report shows the presence of total coliform bacteria, look for the cause, eliminate it if possible, and continue to test the water at an increased You may consider installing a treatment system such as distillation, chemical disinfection, or ultraviolet radiation.

Nitrates

• Test type: EPA Method 300 series
• Frequency: every five years
• If >45 mg/L NO3 or >10mg/L N03-N, install a treatment device or find an alternative water supply. Increase the testing Filtration using reverse osmosis will remove some of the nitrate.

Minerals

• Test type: EPA Method 200 series
• Frequency: every 5 years, or if a change in the water taste or color is detected
• Most water testing companies offer a group minerals test for all listed Be sure to compare the results with previous results.

The levels listed below are set by the California Code of Regulations, Standards for Drinking Water available at: https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/Lawbook.html and https://www.waterboards.ca.gov/water_issues/programs/gama/well_owners.html.

If mineral levels are greater than or equal to these levels, you should consider installing a treatment system or determine an alternative supply of water. An appropriate treatment system is dependent on the minerals to be removed. Consult with a water treatment professional for more advice.

• Aluminum(AI): 020 mg/L
• Arsenic (As): 01 mg/L
• Barium (Ba): 0 mg/L
• Cadmium (Cd): 005 mg/L
• Chromium (Cr): 05 mg/L
• Fluoride(F): 0 mg/L
• Iron (Fe): 3 mg/L
• Lead (Pb): 015 mg/L
• Manganese (Mn): 05 mg/L
• Mercury (Hg): 002 mg/L
• Selenium (Se): 05 mg/L
• Silver (Ag): 1 mg/L

Petroleum

• Test type: Petroleum hydrocarbons by EPA Method 8015 and BTEX/MTBE by EPA Method 8260
• Frequency: every three to five years
• There is no drinking water standard for petroleum hydrocarbons. If petroleum hydrocarbons are suspected or detected at all, then the well should also be tested for benzene, toluene, ethylbenzene, and xylenes (BTEX) and methyl tert-butyl ether (MTBE), which do have If petroleum hydrocarbons, BTEX, or MTBE are detected, then a treatment device can be used or you may consider seeking an alternative water supply.

Solvents

• Test type: Organic Compounds (solvents) by EPA Method 8260
• Frequency: every three to five years
• Each solvent has a specific drinking water If solvents are detected, then a treatment device can be used or you may consider seeking an alternative water supply.

Pesticides

• Test type: Organochlorine Pesticides by EPA Method 8080, Herbicides by EPA Method 8150
• Frequency: every three to five years
• Each pesticide has a specific drinking water If pesticides are detected, then a treatment device can be used, or you may consider seeking an alternative water supply.

Volatile Organic Compounds (VOCs) and Semi-Volatile Organic Compounds (SVOCs)

• Test type: Volatile Organic Compounds by EPA Method 2 and Semi-Volatile Organic Compounds by SW-845 US EPA Method 8270E.
• Frequency: after wildfire damage to water system or suspected industrial contamination
• If water pipes, well casings, or other plastic components were exposed to high heat, the water system was depressurized, and/ or wildfire debris entered the water system, the water should be tested for VOCs and SVOCs. VOCs and SVOCs may also be present in water sources impacted by industrial chemicals, fuel-related chemicals, pesticides, and fire retardants. Each VOC or SVOC has a specific drinking water standard. If VOCs or SVOCs are detected, then a treatment device can be used, or you may consider seeking an alternative water

For more information on Drinking Water Contaminants visit

https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/Chemicalcontaminants.html

Questions? Contact Sonoma County Environmental Health staff at (707) 565-6565 during normal working hours, 8:00 AM to 4:00 PM Monday through Friday.