Pumps come in an array of models and sizes. Pumps are available in both submersible and external (out-of-pond models).
Pumps are sized by gallons per hour (GPH) output at one foot of lift or height. Larger capacity pumps are rated by horsepower (hp).
It is recommended that the water in a basic pond be turned between 1 to 2 times per hour. A 500-gallon pond should have at least a 500 Gallon Per Hour pump. When sizing a pump for a pond there are a few other considerations.
How high will the pump have to lift water? Will there be a waterfall, fountain or statuary? Will there be filters? All of these variables reduce the amount of flow, which could affect water quality and clarity.
How to Determine the Right Pump Size.
For every 10 feet of horizontal distance your water travels (can be a waterfall or a water course connecting ponds) you lose 1 foot of head (vertical lift). For every foot of vertical height you lose 1 foot of head. From the example on the right we lose 2 feet of head from the length of the waterfall and 1.5 feet of head from the height of the waterfall. Add these two together to find the total loss of head of 3.5 feet. A pump must be able to circulate the lower pond's volume once per hour. If our lower pond in the example has a volume of 800 gallons, the pump must have at least 800 Gallons Per Hour (G.P.H.). This is the measurement of flow considered at the top of the waterfall (or the start of the water course). If we go to the following chart we look up the column heading "3 ft" and move down the column until we find 350 G.P.H. or the next number higher. If we then go to the column titled, "pump model", we see that the Shott SP500 is the pump that we need.
Selecting the Right Pump For Your Waterfall
For quiet/ standard waterfalls having a 1/8 inch to 1/4 inch film of flowing water, the pump should push 300 Gallons Per Hour (G.P.H.), per foot of waterfall width, at the top of the waterfall.
For a nice flowing/ rushing waterfall the pump should push 1000 G.P.H. perfoot of the width of the waterfall, at the top of the waterfall.