size for a garden pond?
A7. According to pond pump manufacturers, the pump should turn over the pond’s volume at least once every two hours. I don’t know what research they base this on but for now I accept it as a general rule for the average pond. The pump should also be large enough to supply the flow you want for your water features. The height to which you pump the water above the surface of your pond (i.e.the height of your water features) is just as important as the volume of your pond. Pumps used in ponds are “low head” pumps – they lose pumping capacity rapidly as the height to which they pump increases. When buying a pump, you should ask to see a graph of the pump’s pumping capacity against the water’s “head” (height above the pond surface). The pumps I have used never seem to perform as well as the companies claim. That is possibly because of more friction in the pipework and equipment in ponds than in the ideal squeaky-clean laboratory conditions in which the companies do their tests. Usually, I w
