Well Yield and Recovery Rate
A well yield test pumps the well at a steady rate and watches the water level until it stops dropping. The pumping rate at that balance point is the well's yield, measured in gallons per minute (gpm), according to University of Nebraska-Lincoln Extension.
Recovery rate is the other half: how fast the water level climbs back after the pump stops. Together they tell you whether the well can keep up with your house on a busy morning.
How much water a house needs
UNL Extension estimates the average American uses 60 to 100 gallons a day, and suggests 100 gallons per person per day as a planning figure. Daily volume is rarely the problem, though. Peak flow is.
UNL recommends a well system that can meet peak demand for a two-hour stretch, with these minimum flow rates:
| Home size | Minimum flow rate |
|---|---|
| 2 bedrooms, 2 baths | 10 gpm |
| 3 bedrooms, 2 baths | 12 gpm |
| 4 bedrooms, 3 baths | 16 gpm |
| 5 bedrooms, 3 baths | 17 gpm |
Add 2 gpm for each extra bedroom and 2 gpm for each extra bath. An irrigation system is its own load. UNL lists a lawn sprinkler system at 12 gpm by itself.
How a yield test is done
The idea is simple. Pump at a known rate, measure the water level in the well over time, and see whether it levels off or keeps falling.
On a public water system the rules are strict. Virginia's health department, for example, requires a standard test of at least 48 hours, with water-level readings every 5 minutes for the first 30 minutes, every 15 minutes for the next 90 minutes, then hourly. The pumping rate has to hold steady with a stable water level for at least six hours. When the pump stops, recovery readings are taken every 30 minutes for six hours.
A home-sale flow test is much shorter, and that's its weakness. A short test can show that the pump pushes plenty of water while the well slowly drains. Ask the contractor how long they'll pump and whether they'll measure the water level in the well, not just the flow at a spigot.
Pump flow rate is not well yield
These two get mixed up all the time. The pump's rating is what it can push. The yield is what the well can give back. Minnesota's handbook describes a typical home pump as 10 gpm with a 1/2 or 3/4 hp motor. If that pump sits in a well that only recovers a few gallons a minute, it will empty the casing faster than it refills, and you'll see air, sputtering or a pump that cuts out. A bigger pump makes that worse. Our well pump sizing page covers matching the two.
Can a well run out of water?
Yes, in two different ways.
A low-yield well runs short during heavy use, then recovers. Back-to-back showers plus laundry can draw it down, and an hour later it's fine. Shallow wells, which draw on water near the surface, also drop in a dry season as the water table falls.
A well that goes dry for days usually has a falling water table, a clogged screen, or a pump set too high. That needs a contractor to measure the static water level.
Living with a low-yield well
UNL suggests intermediate storage to supplement the supply during peak use when a well can't keep up. A common setup has the well slowly fill a storage tank, with a second pump drawing from the tank to supply the house. Ask a well contractor to price it against a new well.
Cutting peak demand helps too:
- Spread laundry across the week. A standard washer uses 40 to 50 gallons per load against 18 to 28 for a high-efficiency model.
- Look at filter backwash. UNL says a backwashing filter uses 100 to 200 gallons per cycle, so set it to run in the middle of the night.
- Fix running toilets. UNL estimates about 20 percent of toilets leak.
If the pump is short cycling or sputtering during big draws, check low water pressure from a well and air in the water lines before you blame the well.
What a yield test costs
Many home buyers get a flow test as part of a well inspection. HomeGuide lists a flow test among the inspection items and puts a well inspection at $250 to $550. HomeGuide also notes an inspection doesn't judge whether the water table can supply the house over the long term, so a longer drawdown test is worth asking about on a low-yield well.
FAQ
What is a good flow rate for a water well?
UNL Extension recommends at least 10 gpm for a 2-bedroom, 2-bath home and 12 gpm for 3 bedrooms and 2 baths. More is better, because some appliances and treatment equipment need extra flow to work properly.
What is a low yield well?
It's a well that can't supply your peak demand straight from the ground. UNL says intermediate storage can supplement the supply during peak use.
Will my well run out of water?
A healthy drilled well rarely runs dry for good. Short shortages during heavy use usually mean low yield. Shallow driven wells draw from aquifers near the surface, so watch them in a dry season. Have a contractor measure the static water level if it keeps happening.
Can a drilled well run out of water?
It can, though it's less common than with shallow wells. A falling water table, a clogged screen or a pump set too high can all leave a drilled well short.
Sources
- University of Nebraska-Lincoln ExtensionPrivate Drinking Water Wells: Planning for Water Use (G2149) (opens in a new tab)
- Virginia Department of HealthWell Yield and Drawdown Pump Test Procedures (HTO/007/2015) (opens in a new tab)
- U.S. EPALearn About Private Water Wells (opens in a new tab)
- Minnesota Department of HealthWell Owner's Handbook: A Consumer's Guide to Water Wells in Minnesota (opens in a new tab)
- HomeGuideHow Much Does a Well Inspection Cost? (opens in a new tab)