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Picking the Right Pump

By: Dr Gareth Evans - Updated: 24 Oct 2012 | comments*Discuss
 
Pump Capacity Height Filter Fountain

Nothing livens up the pond – or the whole garden, for that matter – quite so much as a little moving water. Whether you are planning to add a fountain or waterfall, of some combination of both, once you’ve settled on the general look that you’re after, the most important part of the job remains; picking the pump.

As a quick trip to even the smallest of garden centres will reveal, there are plenty of different kinds, sizes and prices to choose from, and should you take a look at some of the specialist suppliers’ catalogues or sites, you’ll find there are still more to tempt and confuse you. With so much on offer, it can sometimes seem hard to know what to go for, but the good news is that if you just think things through calmly, the right pump should pick itself!

What Do You Want to Do?

The kind of moving water feature that you are trying to create obviously has a big influence on the type of pump you need. While a small, low-powered pump is ideal for bubble fountains, or container water gardens, for instance, once you get above the likes of a half-barrel or patio pond, you’ll need something a bit different and more expensive – and it’s not just a question of size.

Unsurprisingly, pond water is seldom what you might call clean – no matter how well you maintain yours – and re-circulating large volumes containing all those particles of silt and vegetable matter, not to mention resident pond life, can cause all sorts of problems to the internal workings of a simple pump over its lifetime. It doesn’t do a lot for the tiny spray holes in fountain heads either. Make the right choice of pump, however, and these problems largely disappear.

Look for a robust pump that has a big pre-filter section – a grown-up version of that little sponge found on smaller units – which will stop any solid particles from entering the body of the pump itself and damaging its moving parts. This kind of pump is particularly well suited to fountains, stopping the all-important spray head from becoming clogged up with quantities of water-borne debris. It’s an ideal all-rounder, and can also drive a waterfall or cascade very effectively, making it suitable for most gardens.

If, however, you are planning a really large waterfall feature, which can tolerate slightly muckier water if it means keeping a large enough volume flowing, then you might get the best results from one of the so-called “solids-handling” pumps. Named after their ability to tolerate small particles suspended in the water, they were originally intended to provide the kind of pumping power necessary to meet the high-throughput demands of bio-filters and their reliable, low-maintenance design has won them many fans. If you’re trying to create a feature to rival Niagara, then this kind of pump certainly calls for some serious consideration.

Calculate the Capacity

Many pond owners have been disappointed when the end result of all their efforts has turned out to be a bit of a trickle rather than the raging torrent they had been envisaging – but fortunately, there is an easy way to ensure that yours doesn’t let you down. It just calls for a few simple calculations first – but don’t panic; even if you harbour a life-long fear of maths, it really isn’t difficult.

  • For fountains – check the box to find the maximum height that the pump can send water. Work out the difference between this figure and the depth of your pond where the pump is to be located and you how high your spray will reach above the surface. If you’re planning to use a fountain statue or ornament, do bear in mind that you’ve just calculated the height above the water’s surface – not from the top of the nozzle! Remember to allow for the length of hose running up inside, and buy a larger pump if necessary. As a general rule of thumb, the greater the pumping height, the more impressive the fountain will be.
  • For waterfalls and cascades – the pump’s capacity should also appear on the box, and is usually given in litres per hour (l/hr). Armed with this, and the width of your waterfall, it’s very easy to work out if the pump you’re thinking about will be up to the job.
  • As a bare minimum, you need a pump that will supply 150 litres of water per hour for every 1cm of waterfall width – so for a small feature 15cm across, you should be looking for a pump capable of delivering at least 2,250l/hr, and double that for a 30cm-wide waterfall.

If you know what kind of feature you want to have, and how much water that means you need to move, picking the right pump could hardly be easier – and best of all, you should end up with everything looking exactly the way you imagined it.

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