Well Recovery Rate Calculator
You pumped water out of the well and timed how long it took to come back. This turns those two numbers into a rate, tells you how it compares to what a house normally needs, and works out how long a shower can run before the well runs dry. Nothing uploaded.
Where your rate sits
Supply against household demand
How long each fixture can run ?
Continuous flow test
Try a different draw
Your well as a tank
Learn more: reading a well recovery test
What the number actually measures
The whole calculation is one division. Gallons the well put back, over the minutes it took to put them back. Pump out 50 gallons, watch the level climb back to where it started after 45 minutes, and you have 50 divided by 45, which is 1.11 gallons per minute.
That is inflow through the rock into the bottom of the well. It is not what your pump delivers, and the two get mixed up constantly. InspectAPedia states the distinction directly: "The well flow rate or recovery rate is not equal to the well pumping rate."
The recovery rate belongs to the aquifer. The pump rate belongs to the equipment bolted to the end of your wire. Put a 10 GPM pump on a 1 GPM well and you have a 10 GPM pump that runs dry, which is a worse problem than a slow one.
Where your rate sits against published standards
The same InspectAPedia page collects the residential figures. It reports that "a well yield of 5 gallons per minute of sustained flow is considered adequate for a one family residence," with "a typical minimum acceptable well yield is 3 gallons per minute, or in some jurisdictions, 5 gpm." Those two numbers are the 3 and 5 GPM marks on the comparison bar above.
FHA writes the same idea as a duration test rather than an average. Each home must be assured of at least 3 GPM over a continuous 5 hour period, rising to 5 GPM for proposed construction. That is what the continuous flow test card checks, and it is a harder test to pass than a daily total.
Falling under those figures does not condemn a well. The same source notes some authorities accept yields down to 2 GPM where 1,500 gallons or a similar quantity of on-site storage is provided, which is exactly the trade this calculator makes visible. Below 1 GPM you are into what Epp Well Solutions calls a low yield well, "producing less than 1 gallon per minute".
The casing is a tank, and that is what gets you through a shower
Water already standing in the well pipe is storage you can spend faster than the well refills. Working out how much is pure geometry: the area of the casing bore times its height, converted at 7.48052 gallons per cubic foot.
A 6 inch casing has a 3 inch radius, or 0.25 feet, so a one foot slice holds pi times 0.25 squared times 7.48052, which is 1.47 gallons. A 4 inch casing holds 0.65. With 100 feet of water standing above the pump, that 6 inch well is sitting on about 147 gallons.
Now the run time. A fixture drains that column at the difference between its flow rate and the well's inflow. The EPA gives standard showerheads as 2.5 gallons per minute, with WaterSense labeled heads at "no more than 2.0 gpm". On the 1.11 GPM well above, a standard head takes 2.5 out and gets 1.11 back, so the column drops by 1.39 gallons a minute. Divide 147 by 1.39 and the shower has about 106 minutes in it, which the tool shows as 1.8 hours.
Swap in a WaterSense head at 2.0 GPM and the deficit falls to 0.89, stretching the same 147 gallons to roughly 165 minutes. The well did not change. Only the tap did.
Why the 24 hour figure is the optimistic one
Multiplying your rate by 1,440 minutes gives a daily yield, and it usually looks reassuring. That 1.11 GPM well returns about 1,600 gallons a day, against the roughly 300 gallons a four person household uses at the EPA's figure of "more than 300 gallons of water per day at home" for the average American family.
Treat that surplus carefully. A recovery test measures inflow while the water level is drawn down, and a low level is when a well recharges fastest, so the rate you measured is closer to a best case than an all-day average. It also says nothing about seasonal decline, which is what turns a comfortable August well into a dry September one.
The continuous flow card is the more honest read. Storage plus inflow over 5 hours on that well comes to 147 plus 333, or 480 gallons, where a 3 GPM standard over the same 5 hours asks for 900. The daily total passes easily and the five hour test fails by 420 gallons, and the five hour test is the one that matches how a household actually uses water.
FAQ
Is the recovery rate the same as my pump's GPM?
No, and confusing the two is the most common mistake with this measurement. InspectAPedia puts it plainly: the well flow rate or recovery rate is not equal to the well pumping rate. Recovery rate is water entering the well from the surrounding rock, which is a property of the aquifer. Pump rate is water your pump can lift out, which is a property of the equipment. A 10 GPM pump on a 1 GPM well will empty the casing and run dry, and the pump specification tells you nothing about how long that takes.
What counts as a good well recovery rate?
InspectAPedia reports 5 gallons per minute of sustained flow as adequate for a one family residence, with a typical minimum acceptable well yield of 3 gallons per minute or 5 in some jurisdictions. FHA asks for at least 3 GPM over a continuous 5 hour period for an existing home and 5 GPM for proposed construction. Below those figures a well is not automatically unusable: some authorities accept down to 2 GPM where 1,500 gallons of on-site storage is provided. Epp Well Solutions treats anything under 1 GPM as a low yield well.
My daily total looks fine so why does the water still run out mid-shower?
Because a day of water and a minute of water are different problems. A well at 1.11 GPM returns about 1,600 gallons over 24 hours, far more than a four person household uses, but a standard 2.5 GPM showerhead takes water out faster than 1.11 GPM puts it back. The gap comes out of the water standing in the casing, and once that column is drawn down to the pump you get air regardless of the daily figure. On a 6 inch casing with 100 feet of standing water, roughly 147 gallons, that shower lasts about 106 minutes before the level reaches the pump.