Last updated Dec 2017
Do you need a pump for a garden pond?
Types of pump for a garden pond
Submersible pumps for garden ponds
External ‘dry’ pumps for garden ponds
Dual-use (submersible and external) pumps for garden ponds
Garden pond pump maintenance
Flow rates and cost calculations for garden pond pumps
Do you need a pump for a garden pond?
Yes, if you’re a water gardener who wants the sight and sound of moving water – either a fountain or a waterfall.
Yes, if you’re a fish keeper (and especially a Koi keeper) who needs to feed the filters, circulate pond water and aerate it.
Pumps draw in water and push it out again by means of an impeller, which is driven by a motor. Apart from a few solar-powered versions, most pumps run on mains electricity at 230 volts, with some stepped down to a lower voltage. Solar power means no worries about cables or electricity, and can be used for pond fountains and air pumps, and self-contained water features. Bradshaws Direct has solar fountain pumps; Pondkeeper has these and solar air pumps.
Types of pump for a garden pond
There is a wide range of pumps available (see Bradshaws Direct or Pondkeeper, but they all fall into one of three categories: submersible, external or dual purpose. You must decide which type of pump best suits your needs – easier if you visit suppliers with display ponds, so you can find out how your favourite effect has been achieved.
Technical terms abound and pump head is one that might puzzle you. It refers to the lift of water to a certain height (9m/30ft is the maximum possible) achieved by the pump. The height is the vertical distance between the water’s surface and the top of the fountain or waterfall.
Submersible pumps for garden ponds
Submersibles are suitable for fountains, filters and waterfalls, and simple and easy to install. All you do is place them in the water at the recommended depth.
Basic pumps (from Bradshaws Direct or Pondkeeper) incorporate a fountain jet with an adjuster to control the height of the jet.
More versatile pumps have another outlet for a hose to supply a filter, waterfall or spout. Fit the outlet with a T-piece (from Bradshaws Direct or Pondkeeper) and you can supply two of these, or use two smaller pumps instead to supply each one separately.
Fountain pumps are fitted with foam pre-filters to screen out particles that could damage the pump and block fountain jets. These pre-filters need frequent attention, but can be swapped for a Uflo version by Rotorflush that reduces the maintenance considerably. Update: this product has been discontinued but you might find a second-hand one via eBay or Gumtree
Other pumps available, known as all-in-one pumps or filters, include a pump, filter and ultraviolet clarifier (UVC) unit. These are available from Bradshaws Direct and Pondkeeper.
Alternatively, choose a direct-drive (also called sump or solids-handling) submersible pump, which costs more than the other pumps, but can cope with particles up to 10mm (0.4 inch) depending on the model (e.g. from Bradshaws Direct or Pondkeeper). These more powerful pumps are good for taking coarse material to an external filter, and for driving a waterfall. If you use one in a murky pond, fit a pre-filter to prevent the fine jets from blocking up.
External ‘dry’ pumps for garden ponds
So-called dry pumps, mains powered air-cooled externally sited, are ideal for handling large volumes of water, so are well suited to a Koi pond. However, they do have higher running costs than submersibles.
External pumps must be operated in cool, dry surroundings, such as an outbuilding or an insulated, weatherproof but well ventilated chamber. For unobtrusiveness and temperature control you could dig a pit in the ground, but it’s also possible to disguise an above-ground chamber using trellis, decking, rockery or whatever else is appropriate to the pond’s setting.
Many fish keepers, especially Koi keepers, choose to use industrial-grade central-heating pumps because of their silent operation, reliability, and relatively low cost. Despite this, manufacturers and suppliers do not encourage this method. If you do choose this option, it is recommended that you install an electronic float switch stepped down to 12 volts to avoid electrocuting the fish if a short circuit occurs. The float switch will protect the pump by switching it off if the pond water levels drop dramatically as a result of leakage or evaporation. For dry pumps designed for ponds, see Bradshaws Direct and Pondkeeper or specialist koi equipment suppliers.
External pumps need filling with water before use (a method known as priming), but if the pump is below the pond water level, gravity will do this for you. Unless it’s a self-priming type, once you’ve positioned it above the water level, you’ll need to prime it by using a footvalve on the inlet tube. And even self-priming pumps need you to fill them with water initially.
Dual-use (submersible and external) pumps for garden ponds
Some submersible pumps can also be used externally because they are cooled and lubricated by the water that they pump. They shouldn’t overheat if they are stored in a dry, well-ventilated place out of direct sunlight.
Pumps of ten watts or more are often fitted with thermal overload cut-outs that trip at around 38 degrees centigrade and will survive overheating. However, smaller pumps without cut-outs should trip a circuit breaker before they begin to melt.
The advantage of dual-use pumps is that they don’t need a weatherproof chamber, but you might want to place them inside a box for sound insulation. If you do this, take extra care because there is no cooling device beyond that of the water flowing through, and these pumps should be given plenty of ventilation.
Garden pond pump maintenance
Pumps need regular attention during the Koi keeping season and need to be removed for annual servicing. External pumps need less maintenance than submersibles, but only if they’re installed and housed correctly. It’s essential to house the pump in somewhere cool and dry with good air circulation.
Keep filter chambers clean to avoid over working the pump, and your pump will last longer in a clean pond because wear and tear on the seal will be reduced. You may have to send your pump off for maintenance, because the seal keeping the motor dry is usually replaced by the manufacturer. With this in mind it’s worth having spare pump parts (from Bradshaws Direct and Pondkeeper) and filter parts Bradshaws Direct and Pondkeeper), to keep seal wear to a minimum.
Submersible pumps are clipped together for easy cleaning and servicing. The bearings will wear down due to debris and limescale, so they need replacing annually. If you live in a hard water area you can save wear on your pump by adding a water softener to a self-contained water feature. If you keep Koi ensure the descaling method you choose won’t harm your fish.
Flow rates and cost calculations for garden pond pumps
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.