If you are eyeing an estate or small ranch in Glen Ellen, your deal lives or dies on water. Private wells can be excellent sources, but performance and quality vary by location and geology. With the right due diligence, you can confirm capacity, plan storage, and protect your investment. This guide shows you how to evaluate a Glen Ellen well from yield to water quality, where to find records, and when to bring in experts. Let’s dive in.
Why water due diligence matters
Glen Ellen spans the Sonoma Valley floor and surrounding foothills. Wells in the alluvial valley bottom often behave differently than those in fractured bedrock or volcanic units on the hillsides. Alluvial settings typically support steadier yields and easier recharge. Fractured rock can produce variable flows, quicker drawdown, and longer recovery. You should never assume uniform performance from one parcel to the next.
Local groundwater responds to rainfall, stream infiltration from Sonoma Creek and tributaries, and irrigation return flow. Seasonal droughts, landscaping or vineyard demand, and clusters of nearby wells can add stress in some pockets. Check basin updates and monitoring data through Sonoma Water groundwater updates to understand current conditions.
If you want a deeper primer on how aquifers behave, the USGS groundwater basics page is a helpful starting point.
Proving well capacity: yield testing
Test types you should know
A yield or pump test measures how much water a well can deliver sustainably and how the aquifer responds. Short tests run 1 to 4 hours and can be useful as a quick screen. In fractured-rock settings, short tests can be misleading. For confidence, especially where irrigation or livestock are planned, use an extended test of 24 to 72 hours or longer. Continuous measurements during pumping and recovery help you understand sustainable rates rather than just peak bursts.
Key outputs you want include the pumping rate in gallons per minute, static water level before the test, drawdown over time, minimum water level during pumping, and recovery after shutoff. Those numbers inform household capacity, irrigation feasibility, and storage needs.
What to collect and who to hire
Have a licensed pump contractor conduct the test and consider a hydrogeologist or qualified engineer to interpret results when risk is moderate or high. Ask the seller for everything on file: the well completion report, any prior pump test, pump installation details, service records, water quality lab results, and as-built diagrams for storage and piping.
If the well log is missing, search the California DWR Well Completion Reports. For local standards and potential septic records, check Permit Sonoma well standards and records.
How to read results for your use
- Domestic-only use can run on modest sustained rates if storage is properly sized. Many single-family households operate on a few gallons per minute when storage and pressure systems are set up well.
- Small ranches, irrigated landscaping, or multiple structures add demand. For irrigation, estimate the needed flow in gallons per minute and hours per day, then compare that daily volume to the sustainable yield plus the storage you can cycle.
- If the test shows slow recovery or erratic drawdown in fractured rock, get a hydrogeologist to interpret the curve and consider a longer test.
Storage and system design
Why storage matters
Storage bridges the gap between your well’s sustainable yield and your peak use. It also adds resilience during outages and seasonal variability. With smart storage, even a modest well can support significant intermittent use.
Components to inspect
Look at the storage tanks, pressure tank, wellhouse, pressure and flow switches, gauges, and any distribution or booster pumps. Note any treatment equipment such as chlorination, filters, softener, or UV. Confirm backflow prevention and check tanks for corrosion, leaks, clear labeling, screened vents, and proper overflow and drainage.
Right-size your storage
- Household indoor use often ranges from about 50 to 100 gallons per person per day. Rural estates can use more, especially with outdoor demand.
- Keep 1 to 3 days of emergency storage for household needs. Increase that for livestock or irrigation.
- If sustained yield is low relative to peak demand, increase storage capacity and run the well when demand is low to refill tanks.
A simple planning approach:
- Estimate daily household use, then add livestock and irrigation volumes.
- Determine how much your well can pump each day, using sustainable gpm multiplied by minutes per day you plan to run the pump.
- If demand exceeds daily well production during peak periods, size storage to cover the difference.
Water quality you can trust
What to test before you close
Private wells are not regulated as public systems. You must request testing. Start with a broad initial panel: total coliform and E. coli, nitrate, general minerals such as TDS, hardness, and sulfate, and metals including arsenic. Add volatile organic compounds if there are risk factors like nearby fuel tanks or historic agricultural chemical storage. See the State Water Board private well testing guidance for what to test and why.
Arsenic has been documented in parts of Sonoma County. Nitrate can be a concern near septic or agricultural areas. Iron and manganese often affect taste and cause staining. Use a California-certified laboratory and follow sampling protocols carefully.
How to sample the right way
Collect from a representative cold-water tap, typically the kitchen, and follow lab instructions for containers, preservation, and hold times. Chain-of-custody for coliform samples is time sensitive. To find a lab, use the directory of California certified drinking water labs.
If results show contaminants, resample to confirm. Inspect wellhead integrity, look for nearby sources, and evaluate treatment options with a qualified professional.
Treatment at a glance
- Microbial issues can be addressed with disinfection and by correcting sanitary defects at the wellhead.
- Nitrate can be treated with reverse osmosis at the point of use or whole-home systems sized to your flow.
- Arsenic treatment uses adsorption media or membrane systems sized to household demand.
- Hardness, iron, and manganese are commonly treated with softeners or specific filters. Have a professional confirm sizing and maintenance needs.
On-site checklist for buyers
Documents to request
- Well completion report and any pump tests
- Pump installation details and maintenance records
- Recent water quality lab reports
- As-built site plan showing well, septic, storage tanks, and piping
- Shared-well agreement or easement, if applicable
Visual and operational checks
- Verify a sanitary, secure well cap and a tidy, protected wellhouse
- Scan for wet areas or pooling near the well or septic
- Look for potential contaminant sources within 100 to 300 feet, such as fuel tanks, barns, pesticide storage, corrals, orchards, or leach fields
- Identify storage tanks, labels, and estimated capacity
- Note treatment equipment, pressure gauge readings, and overall condition
- Run an outside hose bib or laundry tap to observe steady pressure, knowing this is not a substitute for a formal pump test
Copyable quick list
- Request well log and pump test
- Ask for recent water quality lab report
- Check well cap, wellhouse, tanks, and pressure system
- Run a tap to observe pressure and apparent flow
- Look for contamination risks within 100 to 300 feet
- Identify storage tanks and estimate capacity
- Confirm electrical connections and pump controls
- Ask about system age, maintenance, and any low-flow events
When to call experts
- Licensed pump contractor or driller: when no recent pump test exists, when equipment condition is uncertain, or when you plan changes to well use
- Hydrogeologist or professional geologist: when fractured-rock behavior is complex, when wells may be interfering with each other, or when you need a resource assessment for irrigation plans
- Water quality specialist or engineer: when tests show nitrate, E. coli, arsenic, or VOCs and you need treatment design
- Septic designer or site evaluator: when septic proximity or performance is a concern
- Real estate attorney: for shared-well agreements, easements, and transfer documents
Always confirm California licensing, Sonoma County experience, references, and insurance.
Contract strategy and risk management
- Include water quality and pump test contingencies that allow time and access for formal testing and expert review.
- Request disclosure of known well repairs, low-flow events, or water quality issues where allowed.
- Tie irrigation or livestock plans to verified sustainable yield and storage. If the well’s performance is uncertain, budget for storage upgrades and schedule a longer pump test.
Local records and where to look
Final thoughts
In Glen Ellen, well performance is site specific. A quick flow check is a start, but buying decisions should rest on a formal pump test, clear storage planning, and a comprehensive water quality screen. With the right team and records, you can quantify risk, size your system correctly, and protect long-term enjoyment of the property.
If you want a confidential, pragmatic second opinion on a Glen Ellen estate or ranch, connect with Mark Stornetta for guidance grounded in local land knowledge and technical due diligence.
FAQs
What is a good well yield for a Glen Ellen estate?
- It depends on use, but many households function on a few gpm if storage is adequate, while small ranches or irrigation plans often require higher sustained rates or larger tanks.
How long should a pump test run in fractured rock near Glen Ellen?
- Plan for an extended 24 to 72 hour continuous test with recovery measurements so you can evaluate sustainable yield rather than a short-term surge.
What should I test my private well for before closing in Sonoma County?
- Start with total coliform and E. coli, nitrate, general minerals, and metals including arsenic, and add VOCs if risk factors exist, using a California-certified lab.
How much storage do I need for a small ranch in Glen Ellen?
- Keep 1 to 3 days of household storage, then add livestock and irrigation volumes, sizing tanks to cover peak demands that exceed daily well production.
Where can I find the well log for a Sonoma County property?
- Search the California Department of Water Resources Well Completion Reports and request any records from the seller, then confirm local permits with Permit Sonoma.
When should I hire a hydrogeologist for a Glen Ellen property?
- Bring one in when the well shows complex drawdown or slow recovery, when multiple wells may be interfering, or when you need irrigation design confidence.
