Pond Pump Flow Rate Calculator
Calculate the ideal GPH (Gallons Per Hour) for your pond ecosystem.
How to Choose the Correct Pond Pump
Selecting the right pond pump is the most critical decision for maintaining a clear, healthy aquatic environment. A pump that is too weak will lead to stagnant water, low oxygen levels, and algae blooms. Conversely, a pump that is too powerful might create excessive turbulence for your fish or wear out your filtration system prematurely.
1. Calculating Pond Volume
Before sizing a pump, you must know how many gallons of water your pond holds. For a standard rectangular pond, the formula is: Length × Width × Average Depth × 7.48. If your pond is circular, use: 3.14 × Radius² × Average Depth × 7.48.
2. Understanding Turnover Rates
The "turnover rate" is how often the entire volume of the pond passes through the filter in one hour.
- Water Gardens: Should be turned over once every 1 hour.
- Koi Ponds: Require higher filtration; aim for twice per hour (every 30 minutes).
- Wildlife Ponds: Without heavy fish loads, once every 2 hours (0.5x rate) is often sufficient.
3. Factor in Total Dynamic Head (TDH)
The GPH rating on a pump box is usually the "Zero Head" flow rate—what it pumps at water level with no resistance. As you lift water higher or push it through long pipes, the flow rate drops. Our calculator adds 1 foot of "head pressure" for every 10 feet of horizontal pipe to give you a realistic "Total Dynamic Head." Always check the pump's "Performance Curve" to ensure it can deliver the required GPH at your specific TDH.
Example Calculation
If you have a 1,000-gallon koi pond with a 5-foot waterfall and 20 feet of tubing:
- Volume: 1,000 Gallons
- Required Turnover: 2,000 GPH (2x per hour)
- TDH: 5ft (lift) + 2ft (friction from 20ft pipe) = 7 Feet TDH
- Goal: Find a pump that delivers 2,000 GPH at 7 feet of head.