Flow rate is easily estimated by timing the output flow. The time required to fill a quart jar is extrapolated to flow in gallons per hour by the equation:
Second per Quart = 900/x, where x= gallons per hour
Example: How many seconds to fill a quart jar for 25 GPH?
900/ 25 = 36 seconds
Working from seconds: GPH = 900/ seconds
Example: What is GPH if time to fill quart jar is 23 seconds?
900/23 = 39.13 GPH
A liter is about 5% larger than a quart.
Flow calculations are summarized in the table below:
Gallons per Hour vs Time to Fill Quart Jar
| GPH | Time (seconds) |
| 50 | 18 |
| 40 | 22.5 |
| 30 | 30 |
| 25 | 36 |
| 20 | 45 |
| 15 | 60 |
| 12 | 75 |
| 10 | 90 |
| 8 | 112.5 |
| 5 | 180 |