Wednesday, April 23, 2014

How To Determine Your Well Water Flow Rate

Dear Sir,

What is the best way to find out how many gallons per minute my well can pump out? I am looking at putting in an iron filter, but I don’t know if my well has enough flow to backwash it right? I called my well guy and am waiting to hear back from him.

- Bill


This is a good question and comes up a lot. If you have a standard well with a pressure tank and pressure switch, you can use the steps below to determine your well’s flow rate in gallons per minute.
This type of system turns on the well pump at one pressure and off at a higher pressure, usually about a 20 PSI difference.
standard well with pressure tank and pressure switch diagram
Standard Well with Pressure Tank and Pressure Switch
If you have a variable speed pump, or ‘constant pressure’ type pump, that keeps the pressure in the house the same all the time, then this type of method won’t work.  For a constant-pressure type system, consult your well contractor or send us the specifications on your system and we can help you find out what it might be.
well diagram for a typical household
Well Diagram For A Typical Household
Calculate Your Well Flow Rate:
It is easy! All you need is a 1 or 5 gallon bucket and a watch or clock! It takes just a few minutes. Just follow these steps:

1. Open any hose bib or faucet until well pump turns on.
2. Close hose bib or faucet and let pump fill up pressure tank until well turns off.
3. Using a 1 or 5 gal. bucket, open faucet, collect and measure all water discharged until pump turns on. 
You do not have to fill the buckets as fast as you can, simply measure the water.
4. When pump turns on, immediately close faucet and start timing pump cycle in seconds until well shuts off.
5. Divide the number of gallons collected in Step 3 by the number of seconds in Step 4.
6. Multiply the answer from Step 5 by 60.
7. The answer in Step 6 is the average pumping capacity of the pump in gallons per minute (GPM).

If you are still experiencing trouble, try our easy to use pump flow rate calculator on our website!

how to determine pump flow rate on systems with pressure tanks

We hope this information helps you solve your problems, if you have any further questions, or would like to update us on your progress  - we love pictures and testimonials! - you can reach us at or on Facebook. Thanks for the letter!