Measure delivered water flow from a bucket fill test or conventional pressure-tank refill test. These short tests do not establish sustained well yield or water quality.

These short tests measure delivered flow, not sustained well yield or water quality.

Well Water Flow Rate Formula

The following two example problems outline the steps and information needed to calculate the Well Water Flow Rate.

WWFR = G / T × 60
  • Where WWFR is the measured delivery or average pump refill rate (US gallons per minute)
  • G is the collected volume for a bucket test, or usable pressure-tank drawdown volume, in US gallons
  • T is bucket fill time, or pump-on refill time with all outlets closed, in seconds. Do not include pump-off drawdown time.

Divide measured US gallons by the corresponding test time in seconds, then multiply by 60. For the pressure-tank method, use usable drawdown between matching pressure limits and time only the pump-on refill with outlets closed; nominal tank capacity and the entire off-on-off cycle are unsuitable.

How to Calculate Well Water Flow Rate?

The following example problems outline how to calculate Well Water Flow Rate.

Example Problem #1:

  1. First, determine the gallons drawn.
    • The gallons drawn is given as 3.
  2. Next, determine the pump-on refill time with all outlets closed.
    • The pump-on refill time is provided as 20 seconds.
  3. Finally, calculate the Well Water Flow Rate using the equation above: 

WWFR = G / T * 60

The values provided above are inserted into the equation below and computed.

WWFR = 3 / 20 * 60 = 9 (GPM)

Example Problem #2: 

For this problem, the variables required are provided below:

gallons drawn = 4

pump-on refill time with outlets closed = 30 seconds

Using 4 US gallons and 30 seconds gives 8 US gallons per minute.

WWFR = G / T * 60 = ?