Well Yield Test Explained: How Much Water Does Your Well Produce?
📋 In This Guide
Quick Answer: Well yield = how many gallons per minute (GPM) your well can produce sustainably. Good residential yield: 5-10+ GPM. Tested by pumping and measuring water level recovery. Low yield wells (under 5 GPM) need storage tanks or usage management.
What Is Well Yield
Definition
- Gallons per minute (GPM) the well produces
- Rate water enters well from aquifer
- Sustainable over time, not just initial burst
- Key factor in sizing pump and system
Why It Matters
- Determines if well meets your needs
- Affects pump selection
- Guides system design
- Critical for real estate transactions
Factors That Affect Yield
- Aquifer properties (how permeable)
- Fracture connections (in rock)
- Seasonal water levels
- Drought conditions
- Nearby pumping (other wells)
- Well construction (screen area, depth)
Yield vs Flow
- Yield: What aquifer delivers to well
- Flow: What pump delivers to house
- Pump flow can exceed yield short-term
- But can't sustain it
How Well Yield Is Tested
Basic Method
- Measure static water level (before pumping)
- Pump at known rate
- Monitor water level during pumping
- Continue until level stabilizes
- Measure recovery after pumping stops
Duration
- Proper test: 4+ hours minimum
- Better: 24 hours
- Short tests can be misleading
- Well bore storage skews quick tests
What's Measured
| Measurement | What It Means |
|---|---|
| Static level | Water level before pumping |
| Pumping level | Level while pumping (lower) |
| Drawdown | Difference between them |
| Pumping rate | GPM being pumped |
| Recovery | How fast level returns |
Calculating Yield
- If pumping 10 GPM and level stabilizes = 10+ GPM yield
- If level keeps dropping = pumping exceeds yield
- Reduce rate until equilibrium
- That's your sustainable yield
Who Does Testing
- Well drillers (after new well)
- Pump contractors
- Home inspectors (basic)
- Hydrogeologists (detailed)
Interpreting Results
Yield Guidelines
| GPM | Classification | Suitability |
|---|---|---|
| Under 1 | Very Low | Needs significant storage, may not work |
| 1-3 | Low | Marginal, needs storage tank |
| 3-5 | Below Average | Works with management |
| 5-10 | Adequate | Good for most homes |
| 10-20 | Good | Handles irrigation |
| 20+ | Excellent | High demand applications |
Household Needs
- Average home: 100-200 gallons/day
- Peak demand: 5-10 GPM (multiple fixtures)
- With irrigation: Much higher
- Low yield + storage tank can work
What Affects Your Needs
- Number of bathrooms
- Household size
- Irrigation requirements
- Pool, spa
- Livestock, agriculture
Low Yield Solutions
Storage Tank System
- Large tank (1,000-5,000+ gallons)
- Pump fills slowly over time
- Booster pump delivers to house
- Works even with 1-2 GPM wells
Usage Management
- Spread water use throughout day
- Don't run multiple fixtures
- Time irrigation for recovery
- Low-flow fixtures
Well Improvement
- Deepen well (may find more water)
- Hydrofracturing (fracture rock)
- Well rehabilitation (clean out)
- New well at different location
Alternative Supply
- Second well
- Water delivery service
- Rainwater harvesting (supplemental)
We use Hach and LaMotte professional water testing equipment for field analysis, with comprehensive lab testing through certified California laboratories.
Frequently Asked Questions
What is a good well yield?
5-10 GPM is adequate for most homes. Under 5 GPM is low. Under 3 GPM needs storage tank. Over 10 GPM is good to excellent.
How is well yield tested?
Pump at measured rate while monitoring water level. Run 4+ hours until stable. Sustainable rate = yield.
Does well yield change?
Yes—seasonal variation is normal. Drought reduces yield. Long-term declines may indicate aquifer depletion.
My well runs dry sometimes—why?
Pumping exceeds yield. Well recovers between uses. Need to reduce pumping rate or add storage.
Can you improve well yield?
Sometimes. Hydrofracturing, deepening, or rehabilitation may help. Or add storage tank to work with low yield.
Need Yield Testing?
See our water testing services.
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