THE INS AND OUTS OF KOI POND BUILDING
by Mike White, White Water Filters
PART 3: Circulation
In the last installment
we discussed circulation a great deal. The reason circulation is
an important topic is that everything that lives in the pond depends
upon circulation or lack of circulation. Water circulation takes
place both in the pond and outside the pond. To circulate water
outside the pond it requires a force on the water to get it to move.
This force commonly is either gravity, a pump or air.
Gravity and pumps
are commonly used to circulate water outside a pond and are usually
used in conjunction with each other. A pump is used to either lift
water above the level of the pond so that gravity can be used to
move it back to the pond. Or a pump sucks water out of a container
attached to the pond, such as a skimmer or vortex settling chamber,
and gravity returns water to the container to replace the water
that has been removed.
Now I would like
to discuss pumps. Pumps are usually classified as one of two types;
submersible and external. Submersible pumps are designed to run
submersed in water. If they run out of water, they will over heat.
They are usually located in the skimmer or in the pond. Most submersible
pumps are filled with oil to transfer the heat from the motor to
the water. They usually have a life span of less than four years
if used in a pond. It is usually not recommended to rebuild submersible
pumps. Submersible pumps are easier to install and less costly.
For these reasons, submersible pumps are used in ponds.
are located outside the pond and are cooled by the air. If an external
pump is submersed in water it will short out the motor. External
pumps use air for cooling. They usually have a life span of 7 to
10 years and normally can be rebuilt with no problem. External pumps
are generally more energy efficient.
the pump used, it should be matched to the application. Another
concern is the amount of energy consumed as the typical pond in
this area runs about 8 months a year, 24 hours a day and seven days
per week. What sounds like a good deal when you buy the pump could
end up not being the case.
How do you determine
what is the best pump for your application? This is not a simple
matter. First you must determine exactly what the application is
and how much water will be required. Then the static and dynamic
head pressure the system will have must be calculated. This can
then be matched to the pump curve and that will determine which
pump will work in your application.
of circulating water is the use of gravity. Gravity is a constant
force that pulls toward the center of the earth. Since water is
a fluid, gravity is always going to try and pull the water to the
lowest point it can flow to until it is contained. Once water is
higher than the pond, as long as there is a path for the water to
flow back to the pond, it will flow there. This is how a skimmer
works or how a waterfall works. If you are using gravity to move
water through a pipe, the sizing of the pipe becomes critical. In
this case you should consult with an expert to make sure the diameter
of the pipe is the correct size. Gravity is the cheapest way to
move water but may not be the most efficient.
Using air to
move water is a very efficient method if moving the water to a very
limited height. The devices used are called air lift tubes. An air
stone is placed in a body of water and then a pipe is placed over
the air stone. The air going up the pipe moves water with the air
out of the pipe. This can move a lot of water.
Why would water
be circulated outside the pond? Some possible reasons could be to
run a waterfall, stream, or filter.
I have discussed
water circulation and equipment extensively for one reason; the
better the circulation, the better the pond is going to operate.
The poorer the circulation, the more problems there will be with
In the next installment I will discuss
1 - Planning a New Pond || Part
2 - Design || Part 3 - Circulation
|| Part 4 - Mechanical and Chemical
Filtration || Part 5 - Biological
Filtration || Part 6 - Biological
Filters - Mats, Pads and Biofalls || Part
7 - Biological Filters - Bead, Tower and Vortex Filters || Part
8 - Fluid Bed, Bio-Reactors and Nexus Filters || Part
9 - Planning for Pond Expansion
©2004 all rights reserved to Mike White