A yield test tells you what your well can actually deliver over time, which decides the pump size, whether you need storage, and whether a property's well meets a lender's requirements. This page explains the measurements, the difference between a flow check and a yield test, and what a useful written report includes.
What does a well pump test measure?
| Term | What it means | Why it matters |
|---|---|---|
| Static water level | Depth to water after the well has rested | The starting point for everything else |
| Pumping rate | Gallons per minute pumped during the test | What the test asked of the well |
| Drawdown | How far the level drops while pumping | Shows how hard the well is working |
| Recovery | How quickly the level returns after pumping stops | Shows whether the well can repeat it tomorrow |
A useful combined figure is specific capacity: the pumping rate in gallons per minute divided by the drawdown in feet. Tracking it over the years helps show whether a well's performance is declining. Penn State Extension: Water Well Maintenance and Rehabilitation [PSU-REHAB source note]
Is a well flow test the same as a yield test?
During a home inspection, an inspector may pump from an outside hose bib for 30 minutes and note the flow every 10 minutes. That is a snapshot and does not measure recovery. A true yield test of static level, drawdown and recovery must be performed by a licensed well contractor. Water Systems Council: wellcare Guide to Evaluating Water Wells (for home inspectors) [WSC-INSPECTOR source note]
How long should a well yield test run?
There is no national standard. Connecticut's public health code sets a minimum yield test of four hours for a new well; its guidance recommends at least 18 hours for wells yielding under about 1 gallon per minute and notes that requirements range from 1 to 24 hours by state and town. It also describes running the well until the discharge stabilizes. Connecticut DPH: Private Well Guidance for Determining Well Safe Yield (2009) [CT-SAFEYIELD source note]
An example of a simpler owner procedure
New Hampshire's environmental agency describes a homeowner procedure for estimating a well's reliable capacity: measure the water level after the well has been idle, pump at 5 gallons per minute for two hours (or 4 gallons per minute for four hours), then check recovery at 30 minutes, 1 hour, 2 hours and 4 hours after stopping. It treats less than 75 percent recovery over a period equal to the pumping time as a sign the supply may diminish after several days of use. NH DES: Determining the Reliable Capacity of a Private Water Supply Well (DWGB-1-13) Use procedures like this to understand your well, not to replace a contractor's test. [NH-CAPACITY source note]
What should a well pump test report include?
Industry contract guidance lists the type of well development and yield evaluation procedures among the items a contract should specify. NGWA: Guidelines for Written Contracts Ask that the report state: [NGWA-CONTRACT source note]
- Date, start and end times, and who performed the test
- Static level before pumping
- Pumping rate, and how it was measured
- Water levels during pumping, at stated intervals
- Recovery levels after pumping stopped, at stated intervals
- Any notes on sediment, cloudiness or changes during the test
Keep it with the well log. It becomes the baseline for future maintenance checks.
Reading a drawdown test result
A short example shows how the numbers fit together. Suppose a well has a static level of 60 feet. During a two-hour test at 6 gallons per minute, the level falls to 100 feet and holds there. The drawdown is 40 feet and the specific capacity is 6 ÷ 40 = 0.15 GPM per foot. After pumping stops, the level rises back to 62 feet within two hours, near-full recovery.
Three things to look at in your own report:
- Did the level stabilize? A level still dropping at the end of the test means the rate isn't sustainable for that long.
- How much water stood above the pump intake? The pump must stay submerged at the planned rate.
- How fast and how fully did it recover? New Hampshire guidance treats less than 75 percent recovery over a period equal to the pumping time as a warning sign. NH DES: Determining the Reliable Capacity of a Private Water Supply Well (DWGB-1-13)
Keep the report. Comparing future tests with it shows whether the well's performance is declining; a yield decrease of 25 percent or more generally indicates rehabilitation is in order. Penn State Extension: Water Well Maintenance and Rehabilitation See how long water wells last. [PSU-REHAB source note]
Using the result
Compare the tested yield with your household's peak demand in how many gallons per minute a well should produce, size the pump to the well in planning a pump for a new well, and if the yield is short, review low-yield well options.
Common questions
How long should a well yield test run?
It depends on local rules and the well. Connecticut's code minimum for a new well is four hours, its guidance recommends longer tests for low-yield wells, and requirements elsewhere range from about one hour to 24 hours. Ask your contractor which standard they follow.
Can a homeowner test their own well's yield?
Some state guidance describes simple owner procedures. New Hampshire, for example, suggests pumping at 5 gallons per minute for two hours and tracking recovery. These give useful information but are not a substitute for a contractor's test.
What is a good recovery result?
New Hampshire guidance treats less than 75 percent recovery over a period equal to the pumping time as a sign that the supply may diminish after several days of use. Ask your contractor to interpret your specific numbers.
Why does a home inspection flow test not count as a yield test?
An inspector's flow test shows what the system delivered over a short period. It does not measure the static level, drawdown or recovery, which is what tells you whether the well can sustain that rate.
Sources & claim context
Citations mark where guidance is grounded. They are general resources dated on retrieval, not guarantees for any property, project, price, licensure, permit or yield. No expert, attorney or reviewer signoff is claimed by this site.
Penn State Extension: Water Well Maintenance and Rehabilitation · Penn State Extension · accessed 2026-10-10
https://extension.psu.edu/water-well-maintenance-and-rehabilitation
Inspection-interval advice differs from NGWA annual recommendation
NGWA (Wellowner.org): Guidelines for Written Contracts · NGWA · accessed 2026-10-10
https://wellowner.org/basics/planning-for-a-water-well/guidelines-for-written-contracts/
Does not prescribe who pays for a dry hole
Water Systems Council: wellcare Guide to Evaluating Water Wells (for home inspectors) · Water Systems Council (wellcare) · accessed 2026-10-10
Guideline distances are not legal requirements; check state rules on who may inspect
Connecticut DPH: Private Well Guidance for Determining Well Safe Yield (2009) · Connecticut Department of Public Health · accessed 2026-10-10
Connecticut example; 2009 publication
NH DES: Determining the Reliable Capacity of a Private Water Supply Well (DWGB-1-13) · New Hampshire Department of Environmental Services · accessed 2026-10-10
https://www.des.nh.gov/sites/g/files/ehbemt341/files/documents/2020-01/dwgb-1-13.pdf
New Hampshire fact sheet; not a substitute for a contractor yield test
Claims are grounded in the dated source notes above; project-specific price, yield, licensure and permit answers require site-specific and local verification.