HOW TO PICK A POND PUMP
Laguna Koi Ponds
All pumps have a flow curve graph which show flow rate at various head pressures.
Head pressure is the waterfall or fountain height plus the friction loss in the plumbing or filter.
Total Head = Vertical Lift + Friction Loss
For example: Pond Pump A delivers 36 gal. / minute at 10 feet of head but only 8 gal. / minute at 23 feet of head.
At 24 feet of head the pump flow shuts off with zero gal / minute. 24 ft. is the maximum head of the pump.
Most graphs are given in gallons per minute, gpm. Multiply by 60 to get gallons per hour, gph.
Most pond pumps are energy savers with low amps. They are high volume but low pressure. They cannot pump very high. The trade off is electricity. If you need to pump high or under great pressure you will need a pump which in general will cost you double or triple the electricity.
Choose a pump which can give you the flow rate you need at the total head pressure of your system.
1) Determine flow requirement of your system. Most ponds need at least one to two pond turnovers per hour through the filter. A 500 gallon pond would require a pump between 500 to 1000 gallons per hour through the filter.
2) Determine visual requirement of your water feature. You may need a bigger pump to satisfy a large water feature. To get an idea how much you need, a garden hose on full blast gives 600 – 900 gals / hour. Hold the hose near your water feature to get an idea of flow. To make a curtain of water you need at least 1000gph per one foot of ledge where the water falls over. A natural splashing fall may only need 600 gph per foot of ledge or weir.
3) Determine vertical lift or the total height of the water feature or waterfall. Measure from the top of water level up.
4) Determine friction loss in the plumbing. Small pipes increase friction loss. Big pipes reduce friction loss. Use a pipe size which is bigger than the inlet and outlet of the pump. 2 inch plumbing generally gives good results. Long sections of pipe increase friction loss. Try to keep your pump and filter close to the pond. Pipe fittings add to friction loss. Do not use sharp 90 degree fittings, use sweeps instead. Refer to the Friction Loss Chart to determine total friction loss.
5) Determine friction loss of the filter. In general, a pressurized filter can add 5-10 feet of head loss minimum. A non-pressurized type filter does not contribute to a significant friction loss. Non-pressurized filters can use smaller pumps.
Once you know how much gallons / hour you need, add up the vertical head plus the friction loss of the system and you can choose a pump based on the pumps flow curve graph.
1) Flow Rate Required _________gph 2) Vertical Lift____________feet 3) Friction Loss_________feet equivalent
Choose between a submersible or external style pump. Submersible style pumps require a good prefilter to keep solid particles out of the impeller. External pumps should use a leaf trap to protect the impeller and act as a priming pot.