Page 68 - Koi Net - On-Line Koi Magazine - Issue 36
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is the pressure that equals a water column of 10 metres may be that a 20m³ pump only moves 2.5m³ to 4m³ of
height. That’s the pressure to overcome the height water per hour. That’s much less than what it takes to
difference. But pressure is also needed to overcome drain the dirt from the pond. The choice of too thin a
the resistance in the piping. pipe is often the biggest cause of dirt accumulation!
So don’t look at the connections of your filters or
Let’s say the piping is 50mm. We need a certain pumps, but decide what you actually want to pump
pressure to squeeze through 20m³ of water per hour. in m³ or gallons of water per hour. Of course, the
That pressure must lift the resistance pressure in the mentioned connections are constrictions in your piping,
piping and then overcome the height difference. A pipe but they have much less influence than complete piping
of Ø 50mm has per metre (!) a counter pressure equal with such a diameter.
to a head height between 0.5 and 0.7 metres of water:
0.05 to 0.07 bar. So if you have 10 metres of piping
When choosing your piping
before and after the pump, including bends, etc.,
that means 5 to 7 metres theoretical head height, Ø 50mm minimum at a pump of 5m³ per hour
or: 0.5 to 0.7 bar.
Ø 63mm minimum at a pump of 10m³ per hour
So if you have 10 metres of pipework before and after
the pump, including bends and the like, this means Ø 75mm minimum at a pump of 15m³ per hour
5 to 7 metres theoretical feed height, i.e.: 0.5 to 0.7 bar.
Ø 90mm minimum at a pump of 20m³ per hour
Now we’re trying to find a pump that with that head
Ø 110mm at pumps that can move more than 20m³ per hour
height (= pressure) could still displace 20m³ per hour
through that 50mm piping, we find that with the pumps
WE NEED A we know in the pond world, this is virtually impossible! THE CHOICE In exceptional cases, it is even beneficial to have
Ø 125mm piping. It is always interesting to have your
CERTAIN There are only a few pumps capable of doing this. We’ll OF TOO THIN situation viewed or calculated before you start. Often
talk about a pump that, with the right piping, can deliver the different installation and/or increase of the piping is
PRESSURE 50m³ per hour. However, they use 500 watts of power. A PIPE WILL much more advantageous than choosing a completely
TO OVERCOME You’re going to notice that in your power bill. The CAUSE THE new filter line.
conclusion is that Ø 50mm piping is absolutely the
THE HEAD wrong choice! BUILD UP OF Let’s talk about the pusher pump we talked about
HEIGHT If we were to make the same calculation with, for DIRT IN YOUR before. Of course, according to the choice of the
thickness of the pipes to the size of the connections of
example, Ø 90mm of piping, we see that per metre
DIFFERENCE the resistance is only 2cm higher and therefore at PIPEWORK the pump or the filter. Often people think that if a pump
has a certain maximum flow (= liquid displacement per
10 metres only 20cm. There are numerous pumps for
hour in litres), this is by definition achieved, regardless
sale with which we can then move that 20m³ per hour
of the choice of piping. This confusion arises mainly
of water in our system.
because a centrifugal pump is then confused in terms
The energy required is therefore more budget friendly. of operation with a push pump. The latter works
Namely, 75 watts instead of 500 watts. By choosing the according to the principle of a cylinder and piston.
right thickness for the piping, you save energy in this
Suppose we have a push pump with a cylinder that can
case: about €€850 = per year while you are still moving
hold 2 litres of water when the piston is in the most
20m³ per hour of water.
extended position. Then 2 litres will be pressed or
We can also approach it the other way around. We start sucked in at each stroke of the piston. Think of your
again from a Ø 50mm pipe that is 10 metres long and bicycle pump, for example. In fact, you make two
has 5 metres head height loss due to friction. Then it movements: pulling out and squeezing away. With each
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