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Unless otherwise stated all electrical items are 220-240 Volts

For individual Pump flow curves when available please link to appropriate pump above.

Please see further down for Information on Total Head Loss


The main water pump is the heart of all our Pond, Aquarium and Quarantine systems.

It is to your fish what our own heart (pump) is to us. By circulating pond water continuously supplying the fish and the purification filter (biofilter) with oxygen that's dissolved in the water. Switch off the pump for more than 3-4 hours and the filter bacteria start to die which means toxic chemicals will build up in your pond water.

This means the selection and choice of the right pump/s to do the job is very important.

The main pond pump being the workhorse of the pond and invariably switched on 24/7 needs to be ultra reliable coupled with low running costs.

Below are a few handy conversions

To convert gallons to litres multiply by 4.54
To convert cu.feet to gallons multiply by 6.23
To convert cu metres to litres multiply by 1000


1. All water pumps need to have a totally flooded suction to avoid cavitation.

2. It is good practice for the suction line to be at least the suction size of the pump and to be as short as possible.

3. When sizing pipes for water pumps, a general rule of thumb is to throttle down going in and throttle up coming out.

4. This becomes more important the longer the suction line is. It is also good practice to slightly incline the pipe up towards the pump this will encourage any air trapped to bleed out through the pump.

5. All joints in the suction line must be completely air and water tight to avoid cavitation

6. If Isolation valves are installed either side of a pump they must always be fully open when pump is in service. Any flow control should be implemented by spill back re-circulation or diversion.

7. If you need a water pump to self prime when installed in a negative head situation a reservoir or strainer basket has to be fitted to render the pump with a flooded suction volume in excess of the volume of the empty part of the suction line at start up.


There is often a misunderstanding with the term self priming, in the belief that you just switch on and away it goes,this is not how it works

All water pumps need a flooded suction at start up, and to this end need an initial prime. They work by pushing water out (Discharge) and in doing so the hydraulic action draws water in to replace this (Suction).

The term self priming refers to the ability of a pump to maintain this prime when switched off for a period of time and then start up again without the need to re-prime. This will become neccessary in any negative head situation such as when installed above the water level.

This is where the strainer basket/reservoir comes into play, in this case acting as a reservoir.

The pipe work layout must be such that the volume of liquid on the suction side of the pump (In the strainer basket / reservoir) is greater than the volume that might be in the empty run of pipe back to source.

The term SELF PRIMING therefor refers to the ability of the pump to reprime and sucessfully start up with a minimal period of cavitation (mixture of air and water in the impellor)


Pumping capacity and Head .............. Total Head Loss

Every pump states MAXIMUM HEAD and MAXIMUM FLOW. What do these bits of information means and why are they pretty useless bits of information?


This means the height at which flow STOPS ... eg if this figure is 6 feet then at a height anywhere between 0 and 5.9 feet there will be some, but different amounts of, water flow. However at 6 ft there will be NONE. The number is only useful for comparing models (and then not very useful)


This happens at the level of the pond surface and is the flow with no pipe attached to the pump. Probably the best practical situation that closely resembles reality is when all you need the pump for is simply circulating the pond contents. In other words there is no lift required and no significant length of pipe attached to the pump

The energy from a pump's motor is shared between flow (actually mass) of water and the height (head) to which it must be pumped. In a real pond situation it becomes a bit more complicated because when water flows through a pipe, or via a "T" piece, "Y" piece bend, fountain nozzle, or through a valve etc some energy is required to overcome friction losses in these different parts of the system.

Because the pump's motor (energy output) is fixed it means that the water flow is reduced for any specific height (Head) pumped, plus any flow restrictions (Total head) .

Important factors for maximum performance

Use widest diameter pipe you can

Use shortest possible pipe length

Do not kink the pipe (a big problem with thin walledplastic pipe)

Do not use valves, T pieces, Y pieces, sharp bends etc in your pipework if you can avoid it.

Prevent build-up of algae inside the pipe by using NON-transparent piping.

When you use stepped connectors cut off the smaller diameter steps.

To totally and accurately specify a pump you need to know 3 things

(1). Volume of water flow required at the end of the line.

(2). Height to which this flow must be pumped

(3). Head (or friction loss) loss due to restrictions in pipe and fittings.

The last component above can be fairly complex to calculate.

In a fairly simple layout (For example pumping into a non preassurised filter system and /or water fall) by adding 20% to the height you wish to pump to will normally be not far off the mark. You would use this new figure. Actual Height + 20% to specify the pump.

Please Note When more diverse and / or complicated layouts incorporating U.Vs, Heaters, pressure filters, valves and bypasses ect. A far greater in depth assessment would be required.

At Coastal Koi we always advise if in any doubt select next size up You can always use a little extra flow, but impossible to gain flow from any given pump.


By collating the above information and equating it to flow diagram (Curves) for any given pump, you will get a fair idea whether your chosen pump is suitable.

We have tried to incorporate flow diagrams in close proximity below the various individual water pump listings.

How To Convert Different Measurement Units

To convert gallons to litres multiply by 4.54

To convert gallons to US gallons multiply by 1.2

To convert US gallons to litres multiply by 3.78

To convert cu.feet to gallons multiply by 6.23

To convert cu.feet to US gallons multiply by 7.48

To convert inches to cm multiply by 2.54

To convert feet to metres multiply by 0.305

To convert pounds to kilograms multiply by 2.2

To convert sq. feet to sq. Metres multiply by 0.093

To convert cu metres to litres multiply by 1000

Of course to convert in the other direction you divide by the factor. For example to convert litres to gallons you would divide by 4.54

Please Remember

All our pices include V.A.T. :

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