Pond Pumps
Author: Barry Goodwin
Selecting pond pumps.
There is a lot of talk about ponds, and filters, and about the large variety of add on equipment that will perform wonders for your hobby, but you seldom hear much about the poor old much maligned pond pump.
The pump is the workhorse at the heart of your pond system.
Choosing pond pumps is not the arbitrary decision that sometimes it seems, for unless you have worked things out very carefully, you could find yourself at a loss to make the exact selection from the available range. It will pay you to work out the water capacity of your pond carefully. Decide what restrictions (if any) that there will be to water flow, and from this calculate the capacity of the pump required to provide the correct water flow around your pond or water feature.
Your first decision might have to be whether to choose a submersible pump, or an external pump and this choice will most certainly be influenced by pond size. External pond pumps normally turn over large amounts of water, making them inappropriate for small ponds, but very useful for large Koi ponds.
Mostly, delivery rates for external pond pumps range from 10101 litres per hour, up to 33000 litres per hour. This means that you will need (hypothetically) pond capacities of between 20202 litres and 66000 litres to be able to use them.
Broadly speaking, the contents of your pond system should be turned over through the filter once every two hours, but there are exceptions to this with some commercial filters. Disregarding for a moment the above exceptions, it does not always follow that your choice of pump should have a design flow of half of the pond capacity. Restrictions such as pipe friction, accessories, etc will all slow the rated flow. To turn your water over at 10,237 litres per hour, you may need a pump rated at 11,375 litres per hour delivery. Always take you dealer's advice here as he will help you to select the correct pump.
A pond that is smaller than 4500 litres capacity will almost certainly not be adequate for the serious housing of Koi. If your pond is smaller than 18,000 litres capacity, then you may have to opt for a submersible pump, and it is better if you know a little about these beforehand. With a small pond you must be extra careful about your choice of pump for you may be operating under conditions that are marginal for Koi.
Look through the pump adverts to see what the rated capacities, and features, of the various units are and before you make your purchase, talk to other hobbyists who may have some good advice to give you. A handy source of information on recommended pump prices and performance is the Buyer's Guide published in Koi Magazine each month. Oase do make submersible pond pumps, the Aquamax range, that may also be run as an external pump, and this is certainly worth consideration.
You should also consider that Koi keeping is a hobby that grows on you, and when the bug bites, then you always want just a little bit more from it. A pond of 4500 litres could a year hence, prove to be too small and you will be rebuilding it. Some Koi keepers progress through ponds one to five,each one bigger and grander than the last one. A lot of money is wasted in this manner and it is always best to go for the biggest pond that you can envisage - right at the start.
The suitability of submersible pond pumps can be initially decided by looking at the design. A pump that has a built in intake filter may be more trouble than it is worth if it is used directly in a Koi pond. It will get very dirty very quickly, need to be removed frequently for cleaning, and it may be better to consider using such a pump only with a 'gravity feed' design of filter. Some people remove intake filters permanently, but the pumps that they are fitted to are not usually rated to handle solids and impellers can be readily damaged by picking up debris from the pond. The wrong pump could also mean that you will not meet with overall success, for pumps that need to be removed regularly for maintenance and intake filter cleaning could get neglected from time to time. Water quality could therefore rapidly deteriorate to the detriment of your Koi. On the other hand, if you are planning a quarantine or growing on system, then such a pump could be ideal.
There are some submersible pumps on the market that do not use intake filters, and which are rated to handle solids of up to 5mm or 10mm, the newer Hozelock Cyprio Titan pumps and the Oase Aquamax pond pumps are a good example of these, and are ideal for Koi pond use. Because this means heftier impellers that are made out of higher tech materials, this can increase the cost of the pump somewhat, but then you don't get anything for nothing.
The cost of your submersible pump is also reflected in its general quality of construction. Many cheaper "power" pumps that are capable of handling solids are little better than "cellar drainage pumps," and when operated continuously at depths of up to six feet they can suffer premature failure of the shaft seal. The subsequent ingress of water will cause them to fail. More than anything, act on the advice of your Koi dealer here as he will sell a large number of pumps, and will only be stocking the reliable brands. He wouldn't be able to cope with a continual stream of broken pumps passing through his hands,
and the word would soon get around about their unreliability.
With external pumps, the choice always seemed to be easier, but there are a lot more designs arriving now, and the choice is getting harder. The Mini Dolphin pumps are extremely powerful, and if you want delivery capacity, and reliability, at an affordable cost, then they are one of the most suitable choices. Sequence pond pumps do have lower wattage pumps in their range, and these give lower running costs. However the lower wattage does mean the Sequence pumps produce less pressure and may not be suitable for applications where water needs to be pumped up more than 5 - 6 feet vertically. They are also not the first choice for long pipe runs with large numbers of bends.
Running submersible pond pumps
- Do not to run them too deep in the water. This puts a lot of pressure onto the shaft's water seal and can cause premature failure.
- Never unduly restrict the outlet of a high powered submersible pump, this will considerably shorten its life.
- Never carry a submersible pump by its electrical lead, This can damage the lead and damage the water sealing.
Running external pond pumps
- Most external pumps are not self priming (if run above the water surface, will not suck up water without
first being primed) and therefore need to be run in a dry chamber that is below the pond water level. - Make sure that pumping chambers are well ventilated, as overheating will reduce the life of pumps.
- Make sure that the filter baskets (if fitted) are kept clean as a blocked basket can cause cavitation and damage the impeller. It can also cause overheating of the pump.
- Make sure that they are protected from water ingress if not weatherproof.
Above all, whatever type of pump that you use, make sure that all of the pond electric circuits are protected by an RCD. This device will detect electrical leakage and protect you from fatal electric shock if a fault should develop in any of your equipment.
For a range of pond pumps, please have a look at our pond pumps page.
Copyright Pets Parade Ltd. 2000