Modern pond pumps are submersible, reasonably priced, cheap to run, reliable and robust. Many manufacturers now produce ‘solid handling’ pond pumps which can more effectively deal with blanket weed and other solids. This means that the pump will not become clogged by e.g. weed as the device has a built in maceration which will chop up the weed into tiny fragments which will safely pass through the system.
Similar technology has been used in waste disposal units and commercial pumps for many years. The main consideration when buying is the volume of water it can pass, usually in liter per hour.To convert to gallons per hour divide liters by 4.8. The volume of water delivered is also affected by the ‘head’ of water ie the height through which the water must be lifted.
The volume delivered per hour at various heights is expressed in a table and as a graph on the advertising or packaging material for that particular pond pump. All pond pumps work in the same way essentially. An electric motor draws water in through an input unit. This has some sort of filter attached to filter out any debris. Solid handling pond pumps may not need a fine filter.
The output unit forces water out under pressure, the flow is adjusted by a flow adjuster screw and the whole unit is attached to a delivery hose. With the addition of a T-piece the pump will operate more than one feature. The function of a pump is to drive an attractive feature and to force the water through a filter which will maintain water quality and clarity.
Pumps come in a wide range of sizes to suit every type of water feature. Before deciding on a pump it is useful to do a few calculations to ensure your pump has enough capacity to provide enough water to make your feature e.g. waterfall, stream or fountain look effective and also to provide a high enough rate of filtration, if a filter is to be used.
To calculate the volume of a regular pool multiply the area (length X width) by the depth. If the pond is circular, or can be seen as roughly two circles the area of each circle can be closely approximated by multiplying the radius squared by 3. If the measurements are in cubic feet then multiplying by 6.25(UK) or 7.5 (US) converts the volume to gallons.
A generally accepted guide to the size of pond pumps needed involve calculating the gallon-age of the garden pond and dividing it by 2. This is the flow rate in gallons per hour that your pump should provide in theory. In practice, however, a well designed pond and biological filter system will easily function well at half this flow rate or even less.
The filter page will give more information on filters and pond pumps. Prices vary from manufacturer to manufacturer and across suppliers but a guide to the prices of a good quality pump with sold handling facilities.