Two wells on the same road outside Cashmere. One pumps 25 gallons a minute all day long. The other struggles to make 3. Same aquifer, half a mile apart, and you’d never know which was which by looking at the wellhead.
That’s why a well yield test exists. It’s the only honest way to find out how much water your well can actually deliver, hour after hour, when you need it. Guessing gets people into trouble, especially around here where summer demand triples and some fractured-rock wells in the foothills barely keep up.
In this guide, we’ll walk through exactly how a well yield test works, what the numbers mean, what’s considered normal in Chelan, Douglas, and Grant counties, what testing costs, and what your options are if your well comes back low. By the end, you’ll know whether you need one and how to read the results like a pro.
What a Well Yield Test Actually Measures
A well yield test measures how many gallons per minute (GPM) your well can produce over a sustained period without drawing the water level down to the pump. That last part matters. Plenty of wells can blast out 15 GPM for ten minutes, then fall on their face once the casing storage is used up.
Three numbers come out of a proper test:
- Yield (GPM): how fast water flows out of the well over the full test, not just the first burst.
- Drawdown: how far the water level inside the casing drops while the pump runs.
- Recovery: how fast the water level climbs back after the pump shuts off.
Think of your well like a bank account. Yield is your income. Drawdown is how deep you dig into savings during a big month. Recovery is how fast deposits refill the account. A well with modest yield but fast recovery can serve a household just fine. A well with big drawdown and slow recovery is living paycheck to paycheck.
One thing a yield test does not measure is water quality. Bacteria, nitrates, and arsenic need lab work, which we cover in our guide to well water testing in the Wenatchee area. Yield and quality are separate questions, and you usually want answers to both, especially during a home purchase.
If you’re not sure what your well produces, or it’s been more than five years since anyone checked, request a free estimate on a flow test and we’ll give you a straight answer with real numbers.
How a Well Yield Test Works, Step by Step
There’s a quick-and-dirty version and a proper version. Both have their place. Here’s how each one goes.
The basic flow test (1 to 2 hours)
This is the standard test for real estate transactions and routine checkups.
- Record the static water level. Before anything runs, we drop a sounder down the casing and measure where the water sits. Say it’s at 40 feet in a 200-foot well.
- Open a hose bib or test port and run the well hard. We bypass the pressure tank when possible so we’re measuring the well, not the tank.
- Measure flow with a calibrated meter or timed bucket. A 5-gallon bucket that fills in 30 seconds means 10 GPM. Simple, but it works.
- Run continuously for at least 60 minutes. The first 15 minutes mostly drain water stored in the casing. The real yield shows up after that, once the well has to keep up on its own.
- Track drawdown during the test. If the water level drops from 40 feet to 90 feet and stabilizes, that’s useful data. If it keeps falling toward the pump, the well can’t sustain that flow.
- Shut down and time the recovery. A healthy well typically recovers most of its drawdown within an hour or two.
The extended drawdown test (4 to 24 hours)
For new wells, irrigation planning, or wells with a history of running dry, a longer pump test under Washington well construction standards tells the full story. The Washington Department of Ecology oversees well construction and licensing statewide, and their well resources are worth a look if you’re drilling new (ecology.wa.gov/water-shorelines/water-supply/wells).
What we’re watching for
The number on the meter is only half the test. We’re also listening and looking. Air spitting from the hose near the end of a test means the water level reached the pump intake. Sand or cloudy water under heavy pumping can point to a failing screen or sediment problems in the well. A pump that cycles oddly during the test sometimes reveals a pressure switch or tank issue nobody knew about.
Here’s a real example. Last August, Karen in Leavenworth was three weeks from closing on a cabin off Chumstick Highway. The listing said “good well.” Our test said 2.5 GPM with 70 feet of drawdown and slow recovery. Not a dealbreaker, but she negotiated $9,000 off the price to cover a storage tank and booster system. The test cost her $350 and saved her a five-figure surprise.
What’s a Normal GPM for Wells in North Central Washington?
Here’s the question everyone asks, and the honest answer is: it depends on your geology and your needs. But there are real benchmarks.
Most lenders and health departments consider 3 to 5 GPM sustained the minimum for a single-family home. The Washington State Department of Health uses similar adequacy guidance for small water systems (doh.wa.gov). Below 3 GPM, a household can still function, but it usually needs storage to buffer peak demand.
A typical family of four uses 200 to 400 gallons a day. Spread over 24 hours, that’s well under 1 GPM. The problem is nobody uses water evenly. Two showers, a dishwasher, and a sprinkler zone running at 6 p.m. can demand 12 to 15 GPM all at once. That’s where yield, storage, and proper pump sizing all have to work together.
Around our service area, here’s what we commonly see:
- Columbia River valley floor (Wenatchee, East Wenatchee, Malaga): 10 to 40+ GPM from sand-and-gravel wells. Some irrigation wells produce far more.
- Foothill and canyon wells (Cashmere, Leavenworth, Plain, Entiat): 2 to 15 GPM from fractured granite and basalt. This is where low-yield wells cluster.
- Chelan and Manson benches: highly variable, 3 to 25 GPM depending on whether the well hit a good fracture zone.
- Quincy and Moses Lake basin: basalt aquifer wells often run 15 to 50+ GPM, though some zones in the Columbia Basin have declining water levels, a trend the USGS has documented in regional groundwater studies (usgs.gov).
Depth doesn’t equal yield, by the way. We’ve tested 500-foot wells making 2 GPM and 120-foot wells making 30. If you’re curious how depth plays into it locally, see how deep wells go around Wenatchee.
Quick reference: what your GPM number means
| Sustained Yield | What It Means for a Home |
|---|---|
| Under 1 GPM | Marginal. Storage tank required, careful water management |
| 1 to 3 GPM | Low but workable with a storage and booster setup |
| 3 to 5 GPM | Meets most lender minimums for a single household |
| 5 to 10 GPM | Comfortable for a family home with modest irrigation |
| 10 to 20 GPM | Strong. Handles large homes, lawns, small orchard blocks |
| 20+ GPM | Excellent. Irrigation-capable, multiple dwellings possible |
One caveat for rural buyers: under Washington’s permit-exempt well rules, what you can legally use isn’t always what the well can physically produce. Our post on permit-exempt wells in Washington explains the limits by county.
What a Well Yield Test Costs
Good news first. Yield testing is one of the cheapest things you’ll ever do for your well, especially compared to what it can save you.
| Test Type | Typical Cost | Best For |
|---|---|---|
| Basic 1-hour flow test | $200 to $400 | Real estate sales, routine checkups |
| Flow test plus full system inspection | $350 to $600 | Home purchases, older systems |
| 4-hour drawdown test | $500 to $900 | Suspected low-yield wells, irrigation planning |
| 24-hour pump test | $1,200 to $2,500 | New wells, subdivisions, water rights work |
Compare that to the cost of getting it wrong. A storage tank and booster system runs $3,000 to $7,000. Hydrofracturing a tight well runs $3,000 to $6,000. Drilling a new well in this region can pass $30,000, and we break that down in our guide to well drilling costs in Washington. A $350 test that informs a $30,000 decision is the best money in the well business.
Dale in Quincy learned this the cheap way. He was about to spend $4,800 replacing his 15-year-old submersible because the house kept losing pressure on summer evenings. We ran a yield test first. The well made a steady 18 GPM and the pump was fine. The actual culprit was a waterlogged pressure tank, a $1,400 fix. The $300 test saved him $3,400 and a pump he didn’t need. If your pressure drops at peak times, a flow test plus a look at the pressure tank should come before any pump replacement.
Want to know what your well is really making? Call (509) 351-8404 and we’ll schedule a test, usually within a few days, same week in most of Chelan and Douglas counties.
What to Do If Your Well Tests Low
A low number isn’t a death sentence. It’s a design problem, and design problems have solutions. Here’s the playbook, roughly cheapest to most expensive.
First, rule out the system
Sometimes the well is fine and the equipment is lying to you. A worn pump, a clogged intake screen, a failing check valve, or a waterlogged pressure tank can all mimic a low-yield well. This is why we test at the wellhead, not at the kitchen faucet. If the well makes 12 GPM but the house only sees 4, the problem is between the two, and well pump repair is usually far cheaper than any of the options below.
Add storage
For genuinely low-yield wells, a 1,500 to 3,000 gallon storage tank with a booster pump is the workhorse solution. The well trickles into the tank 24 hours a day, even at 1.5 GPM, and that’s over 2,000 gallons a day banked. The booster pump then delivers strong pressure to the house on demand. Cost runs $3,000 to $7,000 installed, and it transforms how a low well lives.
Lower the pump or deepen the well
If the static water level has dropped over the years, sometimes there’s usable water below the current pump setting. Lowering the pump is a few hundred to a couple thousand dollars. Deepening the existing well costs more but is often cheaper than starting over.
Hydrofracture
High-pressure water injected into a rock well can open up fractures and boost yield. It works well in granite and basalt, the rock under much of Cashmere, Leavenworth, and Chelan. Results vary, but improvement happens in roughly 90 percent of attempts.
Drill new
The last resort, but sometimes the right one, especially if the old well also has casing or contamination problems.
Marcus in East Wenatchee went the storage route two summers ago. His foothill well tested at 2 GPM with slow recovery, and his family of five was running out of water every Saturday. A 2,500-gallon tank and booster system cost him $5,600. He hasn’t run dry since, and his shower pressure is better than it ever was on the bare well. If your well is showing signs of decline, our post on wells running dry covers the early warnings to watch for.
When to Get Your Well Yield Tested
You don’t need a test every year. You do need one at these moments:
- Buying or selling a rural property. Non-negotiable. Most lenders require it, and every buyer should. Pair it with a full well inspection before buying a home.
- Pressure or supply drops in summer. If July and August bring sputtering faucets, test before you blame the pump.
- Before adding demand. New irrigation zones, an ADU, a shop with a bathroom, or livestock all change the math.
- Before replacing a pump. Yield determines correct pump size. An oversized pump on a low well will pump it dry and burn itself out, a mistake we see constantly on well pump replacement calls.
- Every 5 years or so as a baseline. Aquifer levels shift. A baseline number turns a future “is it worse?” into a measurable answer instead of a guess.
- After a neighbor drills. New wells nearby can affect drawdown in fractured rock. A fresh test documents your well’s performance with a date on it.
Testing in late summer gives you the most conservative number, since aquifers around here are at their seasonal low after irrigation season. If your well can make its numbers in August, it can make them in April.
Ready to put a real number on your well? Schedule your flow test here or call us at (509) 351-8404. Free estimates, licensed and insured in Washington, and we’ll explain every number on the report in plain English.
Frequently Asked Questions
How many GPM should a residential well produce?
Most lenders and health authorities look for 3 to 5 GPM sustained as the minimum for a single-family home. That said, wells producing 1 to 3 GPM can serve a household comfortably with a storage tank and booster pump. What matters is sustained yield plus storage, not the first-minute flow rate.
How long does a well yield test take?
A standard flow test takes 1 to 2 hours on site, including setup, the sustained pumping period, and recovery measurement. Extended drawdown tests for new wells or irrigation planning run 4 to 24 hours. You’ll usually have a written report within a day or two.
Can a well yield test hurt my well or pump?
No, when it’s done correctly. A proper test monitors the water level the entire time and throttles or stops before the level reaches the pump intake. Running a well dry is exactly what we’re testing to prevent, so a careful tester never lets it happen during the test itself.
Does well yield change with the seasons?
Yes, especially in fractured-rock wells around Cashmere, Leavenworth, and Chelan. Static water levels are typically highest after spring snowmelt and lowest in late summer and early fall. That’s why August and September tests give the most conservative, and most useful, picture of what your well can really do.