Page 67 - Koi Net - On-Line Koi Magazine - Issue 36
P. 67
done. The more bends and the longer the pipe, the less The Piping
water is actually moved. With 40mm pipes, this will
logically be even more difficult than using 63mm pipes. It is often claimed that the choice of a certain diameter
Gravity filters also use 110mm or even 125mm pipes. (= average) of the piping should be the diameter of the
The thinner and more complicated your pipes and hose connections of the pump or the filter as a starting point.
system, the less water your pump will actually move. THE RIGHT This is a misconception. These connections do not say
anything about the required diameter of the piping. The
The Pump CHOICE OF piping must fit the net displacement required to drain the
In our ponds we use a centrifugal pump. These are PIPING IS dirt. There are some restrictions. Water is moved under
pressure. This is necessary to bridge the various height
pumps that move the water out with a blades wheel due CRUCIAL differences. But the higher the pressure, the more
to centrifugal force. Because the water is thrown out, a resistance there is. This places requirements on the initial
pressure is created in the centre of that blades wheel. WHEN pressure that a pump must provide in order to move
The pump will suck in the water as a result. A pump DESIGNING enough water at the end of the piping. With a regular
cannot suck in water when it cannot pump it away. In pond pump, that initial pressure is usually not that high.
other words, there should already be water in the pump YOUR POND It is therefore important that you take into account that
so the pump must be placed below the water level and you do not always reach the entire water displacement
therefore be full of water. A centrifugal pump cannot that your pump could reach in an ideal situation.
suck water from a lower basin. For this purpose there
are other pumps such as the displacement pump. We’ll Each pump has a certain pump curve. This tells exactly
come back to this later. what, at what pressure (= head height), the pump can
IT IS VERY theoretically (!) deliver to net water displacement. So if
Coming back to the centrifugal pump, we know that it
only we would just take the description of the pump
IMPORTANT TO spins the water away, and the more it can spin away,
manufacturer or filter as a guide, we could move
ENSURE THAT the more the pressure in the centre of this wheel will considerably less water than what we hoped to achieve.
increase and the more water will be sucked in. You will
THERE IS NOT understand that the easier we make the centrifugal For example, a 20m³ pump with a connection of 1.5" or
TOO MUCH pump to spin the water away, the more pressure is even 2" (1" = 1 inch = 2.54cm) should have sufficient
created and the more water is sucked in. water displacement with a Ø 50mm or even a Ø 63mm
RESISTANCE pipe. At least according to the theory that the connection
It is very important to ensure that there is not too much points are a measure. That’s not right. In addition to the
IN OUR PIPING resistance in our piping. This applies to both the shape and size of the pump housing, the connections to
pressure side and the suction side. This prevents dirt
a pump also have a shared function in terms of the
accumulation in the filter but also in the pond itself. If
maximum pressure with which the water leaves the
that happens, there’s not enough water displacement.
pump housing. They therefore indirectly affect the
Then the dirt remains in the pond or in the piping, while
amount of water that can be moved at a certain head
the goal must be to move that dirt to the filter where it
height (= resistance). There are many other factors
can be removed before the biological stage. Often we
involved, such as the performance of the pump and the
see a solution in the form of an extra flow pump in the
pump housing. These factors are, for convenience, not
pond or extra air dishes to increase movement of the
included in this article because otherwise we will go very
dirt to the bottom drains and through those drains to the
far into the technical matter of the pump.
filter in the hope that it does not still settle in the piping.
They also try to solve this with a more powerful pump or Let’s take a pump that can theoretically move up to 20m³
by using a different kind of filter. In fact, these are short of water per hour. The pump can do that as long as the
term solutions. The right choice of piping is crucial in counter pressure is not above 0 bar. So without any head
this regard. height or any resistance in the piping. A pressure of 1 bar
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