Koi Pond Pump
A modern koi pond pump is designed to run all day long and are very economical. Much more so than they used to be.
There is a large variety of Koi pond pump models to chose from and you will need to know a few details before you choose the correct pump for your Koi pond. In any Koi pond it is advised to turn over the entire water content at least every 4 hours with some people preferring 2 hours. So if you have a 10,000 gallon pond then you will need a pump that can turn 2,500 gallons of water every hour (this is on the basis of turning the pond water over every 4 hours). It is important to know that the pump rating is given at zero head which means the pump is at water level. If your pump feeds water from the bottom of a 4 meter deep pond to the surface then the power needed to lift the water will reduce the flow rate of the pump. A pump will come with a flow rate chart which will show the flow rate at different heights.
If you have pipework connected to the pump with lots of 90 degree bends then the friction created from the water flowing through these bends will decrease the flow rate of the pump. Pipework should be at least 1.5 inches in diameter to prevent to much loss in power through friction. The general rule of thumb and if you do not have extensive pipework is to take 15% off the flow rate. There is no exact way of freely working out the loss of flow rate.
If you want to create a water fall and are lifting the water a reasonable height then you will need to look at the wattage of the pump. A low wattage pump will not have the power to lift the water very well and so look for a high wattage pump and ask the shop assistant for advice. Many pumps will explain on the packaging exactly what they can be used for.