WONDERING ABOUT WELL WATER SAFETY
Rafaela Equils and Brad Morrison
If you are living in a Sonoma County property that relies on private well water, several key questions can help assess water safety and determine whether testing or system improvements may be needed.
Property owners should know when the well was drilled and by whom, as well as the depth of the well, since these factors influence water quality and vulnerability to contamination.
It is also important to determine whether the well’s flow rate has been tested recently, typically measured in gallons per minute (GPM), to ensure adequate and sustainable water supply.
Information about the presence of water storage tanks—including how many tanks are on the property and their storage capacity—is also useful.
In addition, homeowners should identify whether water treatment or filtration systems are installed, what type of equipment is being used, who installed it, and when it was last serviced or maintained.
Homeowners who notice discoloration with their water should also find out what year was the water heater manufactured (sticker) and how many water heaters there are on the property/water system. Sometimes the age of the water heater(s) is a bigger issue than the levels of contaminants in the well water. In addition, older water heaters are more affected by the buildup and corrosion from water than newer water heaters.
Finally, reviewing whether water quality testing has been performed previously, and locating copies of those laboratory reports, can provide valuable insight into past water conditions and guide decisions about current testing needs for contaminants such as bacteria, nitrates, metals, and other substances of concern in private well water.
According to Sonoma County environmental health guidance, the most common well-water contaminants are bacteria and nitrates, which is why these are recommended for frequent testing.
Arsenic does occur sporadically, rather than universally, in some groundwater sources in Sonoma County. Private well owners periodically test for it as part of a baseline mineral or metals panel, especially if:
• the well is deep groundwater,
• the property is in areas with known mineral deposits,
• or the well has never been tested.
Check out these websites for more information
- https://sdwis.waterboards.ca.gov/PDWW/
State Small Water Systems
- https://sonomacounty.gov/health-and-human-services/health-services/divisions/public-health/environmental-health/programs-and-services/state-small-water-systems
Worksheet
Private Well Water Assessment Worksheet (Sonoma County)
Property Address: ________________________________
Owner Name: ____________________________________
Date Completed: _________________________________
1. Well Information
• Year well drilled: __________________________
• Drilling company: __________________________
• Well depth: ________________________________
2. Water Supply (Flow Rate)
• Has flow rate been tested? ☐ Yes ☐ No
• If yes, GPM: ______________________________
• Date of last test: _________________________
3. Water Storage
• Number of storage tanks: ___________________
• Capacity of each tank (gallons): ____________
4. Water Treatment / Filtration
• System installed? ☐ Yes ☐ No
• Type of system: ________________
• Installed by: ________________
• Installation date: _______________
• Last maintenance date: ______________
5. Water Heater
• Number of water heaters: _________________
• Year(s) manufactured: ____________________
• Any discoloration observed? ☐ Yes ☐ N
6. Water Quality Testing History
• Has testing been done before? ☐ Yes ☐ No
• Date of last test: ________________________
• Do you have copies of results? ☐ Yes ☐ No
7. Contaminants Tested (check all that apply)
☐ Bacteria (coliform)
☐ Nitrates
☐ Arsenic
☐ Other metals: ________
