Well Flow Rate Calculator
| 5-gal bucket fills in | Flow | People at peak | Verdict |
|---|---|---|---|
| 20 seconds | 15 gpm | 7 | strong |
| 30 seconds | 10 gpm | 5 | comfortable |
| 45 seconds | 6.7 gpm | 3 | workable |
| 60 seconds | 5 gpm | 2 | practical floor |
| 90 seconds | 3.3 gpm | 1 | one fixture at a time |
Time how long an uninterrupted fixture takes to fill a bucket of known size. The calculator turns that into gallons per minute, compares it against the peak your household actually demands, and reads the margin.
The number people miss is the difference between pump capacity and well yield: the bucket test measures the whole system at that moment, and a well that refills slower than the pump draws will pass a quick test and fail a long shower. Run the test across a sustained draw - thirty minutes, not ten seconds - to see the aquifer, not just the plumbing.
How to use
- Pick one fixture close to the pressure tank - a bathtub spout beats a shower head, which throttles flow on purpose.
- Nothing else running: no irrigation, no washing machine, no ice maker refilling mid-test.
- Time the fill over the longest run you can spare; if the flow fades over minutes, that fade is your well recovery, and the sustained low number is the honest one.
Frequently asked questions
How do I test my well flow rate?
Fill a bucket of known size at one open fixture with everything else off: gallons divided by seconds times 60. A 5-gallon bucket filling in 30 seconds is 10 gpm. Repeat over a half hour of continuous drawing - the sustained rate, not the first minute, is the well talking.
How many GPM does a house need?
Plan on about 2 gpm per person at peak - a family of four wants 8 to 10 to run a shower and a dishwasher without someone losing pressure - and treat 5 gpm as the practical floor for any full-time household. Wells below that support one fixture at a time, not a family.
My well tests fine for a minute, then slows. Why?
That is recovery versus draw: the pump can pull faster than the aquifer refills the well casing, so the first minute measures the storage above the pump and the half-hour rate measures the true yield. Size irrigation and simultaneous fixtures to the sustained number, never the flash one.
Can I fix a low-yield well?
Often, around it: a storage tank charged overnight turns a 3 gpm trickle into morning-scale capacity, fracturing or deepening the well can raise the aquifer rate, and staggered use - irrigation on a timer, not on demand - stretches what is there. The calculator margin shows how far you are from needing any of it.
Does flow rate affect a water softener?
It can: softeners refill their brine tank and backwash at set flows, and on a low-yield well that draw can drop house pressure mid-cycle. Sizing the softener to the true flow rate - the water softener size calculator handles the capacity side - keeps regeneration from stealing your shower.