Top quality hand selected
Japanese Koi Carp at sensible prices

Dormer Cottage, Spurgrove Lane, Little Frieth,

Nr. Henley on Thames, Bucks, RG9 6NU

Phone/Fax: 01494 882600

Order Hotline: 07814 011357

last updated 27th January 2023

Water Pumps


How to choose them and what are the running costs?


At Koi Water Garden, we are able to offer competitive prices on not only high quality koi, but also on koi related goods such as pumps, filters and other accessories.


Which water pump do I use?  and What will they cost to run?


All modern koi pond pumps are designed for 24 x 7 x 365 running and most now have very low running costs. There are however still significant differences between models, so you will need to know certain details of your proposed system to enable you to choose the correct pump. In any koi system it is desirable to turnover the entire contents of your pond through the filter every 2 - 4 hours. So for example if you are building a 5000 gallon pond, you will need a main filter pump capable of delivering at least 1700 gallons per hour (5000 divided by 3). However pump rating are all given at zero head, the height between the pond surface and the point that water is returned to the pond. The more the head, the less the flow rate as more power is required to push water 'up hill' All pumps manufacturers calculate the maximum recommended head for their pumps and will supply a chart giving the final flow rate at certain feet of head pressure.


In addition however you must take into account the pipe work layout of your system - the longer the return pipe work and the more bends present, the greater the frictional flow losses which can occur and the final pump flow can be substantially affected by these factors. We would recommend a minimum pipe diameter of 1.5" (38mm) and if the pipe runs exceed around 10 ft, to increase the pipe diameter to 2" (50mm) to avoid friction losses. Unfortunately there is no easy way of calculating frictional flow losses caused by pipe work but you should always allow for a minimum of 20% performance reduction caused by pipe runs.


Taking these factors into account it is therefore most appropriate to calculate your filter pump requirements based on a 2 hour pond turnover rate, so in the example above, for our 5,000 gallon pond, we would recommend a pump with a design flow rate of 2,500 gallons per hour. Even after allowing for head losses and pipe work losses this should still give us a final flow rate of 1700 gallons per hour at least, so that we are within the guidelines of a turnover rate of between 2 and 4 hours.


If you are looking for a pump to power a water fall or Venturi, then there are different factors to take into account. We don't recommend venturis, as they are very inefficient devices used to pull air into the pond water by forcing the pump to push water through a restrictive venturi tube. Not only is the airflow produced usually too small unless the device is placed right at the surface, but the final pump flow rate can be reduced as much as 2/3rds! - Yes 2/3rds. This means you will need a much bigger pump to power the system than required, just to power the venturi. This increase the initial cost of the pump, the running costs, and importantly will reduce the life of the pump - not an ideal set up!


Waterfalls are a tremendous idea in any koi pond, can look and sound fabulous and provide the most efficient form of aeration. Again however they need a substantial flow rate to look the part and because of head losses, the pumps need to be fairly powerful to achieve the desired result. As an example, a waterfall with a cascade around 18" wide and 3 feet high would need a flow rate of at least 2000 gallons an hour at the cascade to look good. There is nothing worse than a waterfall which dribbles water !


The most important thing to remember with waterfalls and other water features is that it is not only the stated flow rate which is important, but the wattage of the pump. There is a big difference between a 2000 galls/hour flow rate @ 95 watts and a pump delivering 2000 galls/ hour @ 220 watts. The former is classed as a water mover, and whilst excellent for main filtration flow, would not have sufficient power for a venturi or waterfall where back pressure and head are significant factors. The 2nd pump mentioned would deliver the rated flow, overcoming back pressure and would pump up to considerable heights as it is more powerful, but of course more expensive to run.


We feature a range of pumps for koi ponds all of which have specific applications, some dry pumps, some submersible and some dual purpose. You should now however find it easier to choose the correct pump for your application having considered the facts outlined above. We would be happy to help by providing a pump recommendation - just email us at




Water pump
Watts Units (Kw Hours) Units per day Units per Year Cost per Year @ 30p per unit
Oase 4000 65 .065 1.56 569.4 170.72
Oase 6000 90 .09 2.16 788.4 236.52
Oase 8000 110 .11 2.64 963.6 289.08
Oase 11500          
Oase 14000          
Oase 16000 280 .28 6.72 2452.8 735.84
Typical 250 watt Pump 250 .25 6 2190 657.00
Typical 400 watt Pump 400 .40 9.6 3504 1051.12
Typical 500 watt Pump 500 .50 12 4380 1314.00
Air Pump          
Secoh SLL 40 53 .053 1.272 464.28 139.28
Secoh JDK 40          
Secoh EL 100 141 .141 3.384 1235.16 370.55
Secoh JDK 80          
15 watt 15 .015 .36 131.4 39.42
30 watt 30 .03 .72 262.8 78.84
55 watt 55 .055 1.32 481.8 144.54
110 watt 110 .11 2.64 963.6 289.08
220 watt 220 .22 5.28 1927.2 578.16

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