Flow rates

A pump's flow rate is quoted in litres (or gallons) per hour. The ideal flow rate for a fountain or waterfall depends on the effect you want, so you need to read the manufacturer's literature. Remember that manufacturer's figures for pump performance are obtained without any fittings, so obtain specialist advice about the effects of various additions before deciding which pump to buy. For Koi keepers, the rule of thumb is to circulate half of the pond's capacity every hour for the filters to work optimally.

Cost calculations

Calculate running costs by multiplying the charge (on your electricity bill) per unit by the kilowatt rating of the pump for the hourly running cost. For example, if a unit costs 7p, it will cost 50.4p to run a 600 watt pump for 12 hours (7p x 0.6kW x 12 = 50.4).

For pumps rated in horsepower, calculate watts by multiplying horsepower (hp) by 746. For example 0.25hp is equivalent to 186.5watts.