Well test planner: what is due on your well
Tell us when you last tested. We show what is due now, using Sonoma County Environmental Health's schedule.
Where to test
Use a state certified lab. The well testing guide lists five in and near the county. Environmental Health can answer questions at (707) 565-6565, 8 am to 4 pm, Monday to Friday.
The rules behind this
- Bacteria: twice a year, and after a flood or other disaster.
- Nitrates: every 5 years.
- Minerals: every 5 years, or when taste or color changes.
- Petroleum, solvents, pesticides: every 3 to 5 years. This planner flags them at 3 years.
- VOCs and SVOCs: after wildfire damage to the water system, or if industrial contamination is suspected.
Sources
Checked 2026-10-11. Rules and programs change. If something here is out of date, the source above wins. Spot an error? See our corrections policy.
Related reads
Wells and groundwaterHow often to test your well water in Sonoma CountyTest for bacteria twice a year and after any flood. Test nitrates every five years. Use a state certified lab.Updated Oct 11, 2026
Wells and groundwaterCan your yard recharge groundwater?Yes, a little. Rain that soaks in stays in the ground. Paving and fast drainage send it away instead.Updated Oct 11, 2026
Wells and groundwaterRural water systems: wells, tanks, pumps and pressureA rural water system gets water legally, stores it, moves it and pressurizes it. In Sonoma County the state sets water rights and Permit Sonoma controls wells. Most homes use a well pump with a pressure tank, or a pump that fills a high tank so gravity does the rest.Updated Oct 11, 2026