The Pond pump buyer’s check list

If you’re considering building a pond that features a fountain or waterfall, or are looking to install a UVc and filter, then you’ll need a pump.

A pond pump has a demanding role, pumping continuously through a 12 month rolling contract in extremes of temperature, handling unmentionable material. Working hard out of sight in a healthy pond is a pump, at the heart of every pond. If a pond pump were to fail, we would stand to lose more than the soothing effects of a fountain or waterfall. A pump’s lifesaving role is one that supplies the filter (the pond’s liver and kidneys) with toxic material for it to break down. If there is no pump then there will be no filtration which will be followed by a deterioration in water quality and fish health.

As a pump is so vital in sustaining the life of a pond, it is essential that before making such an important purchase that you are aware of all of the necessary information required to make the wisest choice.

Things to consider before purchasing a pond pump.

1. The volume of the pond (including the filter)

A pond’s volume should be turned over at least once every 2 hours. For example, if a pond has a volume of 1500 gallons, a pump capable of pumping 750 gallons per hour would be suitable. But be aware that any extra work that a pump has in pumping water to a filter or waterfall will also significantly reduce the pump’s performance.

2. Work or ‘head’ that a pump has to achieve.

The flow rate of a pump is reduced as soon as a pump has to move water above the water’s surface. The vertical distance between the water’s surface and the delivery height of the pipe is described as the ‘head’ with the greater the head, the greater the work and the lower the pump turnover. Returning to the previous example, if a pond has a volume of 1500 gallons, and requires a turnover of 750 gallons per hour, if that same pond has a waterfall that is 2 feet high, then a suitable pump would be one that provides a turnover of 750 gallons per hour (minimum) at 2 feet of head. This will mean choosing a larger pump than you may have first expected. Check the pump’s specification on the side of the box.

3. When comparing pump performance, make sure you are comparing like with like.

A factor of trading in the EU is that pump flow rates are more often measured in litres per minute rather than gallons per hour. This can cause problems when comparing the performance of similar pumps so be prepared to convert gallons to litres and vice versa.

4. The effect of pipework on flow rates.

Using the incorrect diameter pipework can mean that even having chosen the correct pump, that once installed, it underperforms.

When piping water from a pump up to a waterfall, use as few elbows as possible, tending towards the use of sweeping bends in flexible hose if possible. This will reduce the friction of the water in pipework, improving pump performance. Always use the pipe diameter as recommended by the pump’s manufacturer (even if reducing hose-tail adaptors are provided with the pump) as deviating from the ideal diameter will also reduce pump performance.

5. Running Costs

As a pump is likely to be used continuously, the running cost is a significant consideration when pricing up for a pond pump. Power consumption is measured in Watts with a greater figure relating to a more power-hungry pump. The wattage will not always relate to the overall performance of a pump as efficiencies in design and construction can enable some lower wattage pumps to outperform pumps with larger motors. The difference in running costs over the lengthy lifespan of two different pumps could amount to the price of a new pump.

6. Guarantees and expected lifetime.

Most pumps are now sold with a free extended warranty of anything up to 3 years. With standard maintenance and the use of correct pipework so as not to produce high back pressures, then even these lengthy guarantees can be exceeded.

Most pumps are fitted with foam or perforated plastic pre-filters to prevent impellors from becoming blocked, but these can reduce pump performance even when only partially blocked. Careful positioning within the pond or the selection of a solids-handling pump can help to resolve these problems.

Why have a pump?


As garden ponds are typically stocked with fish above what is natural, the balance of the pond and ultimately the health of the fish are completely reliant on a filter, which must be fed continuously by a pump. A filter performs the functions of trapping solids and breaking down toxic waste produced by fish. The beneficial bacteria that break these wastes down require a steady flow of water to supply them with food and oxygen and to remove their by-products. Whenever a pond does experience pump problems, be they a complete breakdown or a drop in performance, then this is likely to be followed by a change in fish behaviour through them experiencing a deterioration in water quality.

An additional function for the pond’s work horse is to circulate water through an ultraviolet clarifier. This algae-busting hardware must be fed with a continuous supply of water to ensure that the unit works effectively.

Pumps can also be installed with a dual role of both water circulation and aeration, through waterfalls, fountains and ornaments. For a waterfall to look realistic, with the full channel width covered in flowing water, sufficient water must be delivered by the pump to the top. A flow of 500 gallons per hour is usually required for a waterfall 6″ wide and if a pump is not able to deliver this flow, then a waterfall will be a rather disappointing trickle rather than a cascading flow.

Fountains are less demanding for a pump and can easily be installed using an adjustable T-piece with little detriment to the waterfall.

Different Types of Pump.

There are two types of pond pump available to the pond keeper – the external or surface-mounted pump and the submersible pump.

1. External pumps.

External pumps are sited outside of the pond. Such pumps are often referred to as swimming pool pumps and are better suited to larger, more specialist situations where above-average turnover of pond water is required. Consequently, external pumps form a very minor part of the mainstream garden pond market, being better suited to larger more specialist koi ponds.

2. Submersible pumps.

Submersible or internal pond pumps are by far the most popular pond pump. They are extremely versatile, being available in a range of sizes to suit most applications from a tiny fountain pump for a self-contained water feature to a jumbo submersible pump for a large pond complete with waterfall and filter system. They are very straightforward to install and having been developed in a very demanding market are sold with lengthy guarantees.

The only moving part in a typical submersible pump is the magnetic impellor assembly which is driven by an electromagnet which is situated within the main pump body. All of the electric components within the body of a submersible pump are safely encased in hard resin which is itself retained in a robust and water-tight pump body.

Even so, to ensure complete safety, submersible pumps should be plugged into the mains through a ‘RCD’ breaker. Some pump manufacturers produce low voltage pumps which take their current from a transformer, further reducing any risk of a large electric shock.

In summary, a pump is the unsung hero of a garden pond. It is multi-talented, performing both functional and aesthetic roles and having chosen one wisely, should last you several years, keeping your pond and fish in good health.

Kill blanketweed and string algae.