How to Build a DIY Heavy-Duty
Venturi for Direct Aeration of Pond Water
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During my search for information on how to build a DIY
venturi I got in contact with a guy called ZikZ@k (Mark
H) who frequents the American
Water Gardening Society (AWGS) Forums, and who has
kindly given permission for me to include
his
ideas
on
venturi
design, that include an intrigueing "toothed" design.
This page is entirely Zik's own work, combined with information
from
our email
discussion
on
the
subject.
Whereas my "Bio-Filter and
Venturi" project required
a light-duty venturi capable
of operating with a low-pressure water pump into a Skippy
style bio-filter, Zik's designs are for the
more conventional purpose of aerating the water
directly in
the main pond, and therefore can be driven by larger
pumps, producing more intense oxygenation of the water
and giving current for the fish to swim against, and
better circulation of water in the pond.
Zik has prepared
a PDF document which this page is based upon that can
be downloaded by clicking here.
Also read the Additional Hints & Tips section for
extra details and pics not included in the PDF.
Thanks Zik for all your help!
Jim.
This page covers the following topics (click to jump
to them):-
Over to Zik.....
Basic
Venturi Construction for the DIY Crowd
"I have been thinking about this for a
while, doing a small write up and trying to explain
different construction
techniques for a common venturi using fairly
easy to find materials. The materials that I
have used here have been found at several places.
A good hardware store / home improvement center
and the aquarium
store is all it amounts to.
The tools you will need are of common variety. Pretty much general tools such
as a razor knife, an xacto knife, a
triangle file, a drill, etc…
Do be careful with any sharp instrument, tool, or power device. As with
all DIY projects, it is possible to hurt yourself.
I am only showing three designs in this document. I have
made many venturis for many different projects. You do
not necessarily need to use the materials that
I have depicted in this file. My material list changes continually to meet what
I have on hand, as well as what I am trying to accomplish. Using this same basic
design I have made venturis up to 2”.
This file is meant to be public domain. You can use it
how you see fit. Copy
it, pass it around, I don’t care. If you hurt yourself, I didn’t
do it. If you eat the venturi after you make it, the hospital bill for removal
is yours. All responsibility for anyone reading/using this file lies with the
person reading/using this file.
Now, with that out of the way… Some kudos are necessary!
Gene Winstead, the owner of Koi Village gets a plug here. He has been a friend
since shortly after my wife and I got into keeping koi. His help has been appreciated
by both of us.
Kudos go out to Greg Bickal and John Johns for their contributions to the DIY
crowd.
People that post anywhere, sharing their knowledge with the rest of us, you deserve
a plug here too! Special thanks to the members of the Water Gardening Magazine
Forum, and the KoiVet Forum.
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On to the Goodies….
1) This inline ½” venturi goes to a submerged
media filter. It has an adjustable air intake to make
it work properly
above water level.
2) Wider field of view from above to show the air intake.
Notes:
You will notice that I use a wide variety of tubing to
reduce the air intake size on almost all of the venturis
that I make.
It is good to have several sizes of tubing on hand for
a lot of reasons, this is one!
A side benefit to using pressure fit parts is that it
makes the tip adjustable. This is handy for adjusting
the venturi to
your pump, depth you wish to use it at, and amount of
aeration desired.
Keep in mind that the materials used here are not necessarily
the materials you will use. This same principal and
these two designs are meant to be used for demonstration
purposes.
3) 1” venturi with silicone air tubing and an air
stone as an air filter. The body is a nylon 1” coupler
instead of a “T”. I
very carefully cut a hole in the side of this coupler
to be able to pressure fit the tip into it. The silicone
air tubing
works pretty well, but can be prone to kinking as well
as limit the amount of air the venturi can take in. The
air
stone in this picture is being used as an air filter.
4) The tip. Pay
attention to the angles I cut, not just the overall shape
of the tip. These tips are normally
installed so
the point on the end is just off of the bottom of the
venturi body for best suction. For more water flow, just
don’t
slip the tip into the body as deep. For more air push
it in deeper.
5) Another angle of above
6) Another angle of above
7) The feed side
of the above venturi. Water enters here. It does help
to bevel the intake side for a smoother
transfer of water between the tubing you will use, and
the venturi body. At the top you can see the various
tubing I
used for reducing the size. This is so I could use the
silicone airline.
 Top A Venturi with Bite!
Now for a different take on the same basic
idea:
1) Some parts I was considering for making a “toothed” venturi.
From this picture I only used the nylon “T “and
the ½” aquarium riser tube that just happened
to fit into the “T” very
nicely. The clear, flexible tubing does not make
good tips because it is too soft. Mainly I use it
for an air line down to the venturi. The white tubing
is
stiff enough to
make tips from and will resist abrasion well. It is hard
to make the back cut on it if you do not have a *very* sharp
razor type knife.
2)
I tried to represent the depth of the angle on the tubing
in this picture in relation to the opening of
the venturi
body. The clear tubing is “air riser” tubing
that is meant for aquariums. It is semi rigid and resists
abrasion well. As
you can see I sanded a very flat angle onto the end of
it. Sanding it flat so it has sharp edges is important
to
making the tip work well.
3)
Same as above, different angle. Notice the depth of the
angle on the tip. It is roughly the same height as
the hole
it will fill once pushed inside the “T”.
4) Shows the tip
with one tooth cut into it, installed in the venturi
body. This is a good depth to
start at with the tip. All I did to
pressure fit the
tip into the “T” was wrap the tubing with
Teflon thread tape. Tip: wrap some on, then test fit,
wrap some on, then
test fit… Do this until you get it snug, then wrap
a few more layers on and fit it again. Teflon tape compresses
and
may loosen up. If it does, just wrap on some more until
it is snug, but you can still adjust it.
5) This shows a
close up of the modified tip. It has 3 teeth. Note the
angle of the cuts. I used a jeweler’s triangle
file to make the triangle cuts.
It also makes the back side of the angles nicer. The
angle you see in the above pictures were not modified;
only sanded flat and de-burred very carefully so as not
to round the edges. A sharp xacto knife was
used to clean the backside of
the V cuts (on the outside of the tube). If the
V cuts are clean this will create smaller bubbles
than if no V cuts were made. It also provide a longer
edge in contact with the water to create more suction. Double Bonus!
6) A good macro
of the 3-tooth tip. The white stuff is Teflon Tape used
in plumbing to be able to friction fit the
tip into the
valve body. You have to put some on, fit it, and then
add a couple more wraps and fit it again to make teflon
work
for you. It compresses on the first fit. The second
fit will make it hold better. Oh, I should mention
that I
have had
the best luck running deep with these tips. I think
it is because there is more linear edge for the water
pressure
to
act on, creating more suction. You have to have a
semi hard material to make this work though, or the teeth
will
try to fold over on you.
Notes:
Even a single triangle in the center of the tip
will increase the suction. My testing shows
this to be a very aggressive aeration design. However,
it will plug up easier than a tip that has not been modified
in this way.
I used
this with an
1800gph mag drive pump for a long time before going
to a larger version of the same design.
Thats the end of the content in Zik's downloadable
PDF,
but here is some more information.....
To see pictures of my new venturi based
on Ziks design operating in my bio-filter, click here.
Top Additional Hints & Tips
[These further hints and tips arose from
my email discussion with Zik, along with some additional
pictures that he took after dismantling one of his venturis
for the purpose.] Dissolved Oxygen
Running at 2 feet or more really
makes a difference in the amount of O2 that can be
dissolved
into the water.
Venturis dissolve more O2 at a greater depth because
there is more pressure differential.
Bubbles flowing thru
the water give up very little O2 to the surrounding water
because of the skin effect water has. The skin creates
a barrier at the surface of the bubbles. Bubbles
when created or broken will give up O2 to the water.
If this is done
under pressure (like in a large waterfall) it is possible
to supersaturate the water with 02. (Not a good thing,
bad for fish).
Venturis allow for maximum aeration without supersaturation
of the water, or at least not easy to reach those levels
in our situation.
Bubbles
that are created at a deeper point will also cause more surface
agitation and will circulate the water better in the main body of water
if that is where the venturi is used.
As far as efficiency is concerned, venturis are amongst
the most efficient ways to dissolve O2 into water, when
they are designed and applied right. You may wish to
look at this page http://home.att.net/~oxymax/aerate.htm as
it is very informative.
You wouldn’t believe the amount of aeration you
can get from a mag 1800 / 1” venturi combo. Here
are some more pictures to look at.
Note the rubber gators over the jubilee clips. These
prevent the fish from
rubbing against any sharp edges
and hurting themselves.
Venturi Silencers
Note
that I did not show any way of making the venturi quiet.
We use syringes
around here for
taking water from the tanks for easy dispensing into
the testing vials,
so I always have some old ones on hand. I have even used
parts of them
for use in a venturi. I like to
use an old syringe to hold a loosely packed cotton ball
at the intake of
the air tube. (If the cotton gets wet when you turn off
the pump, make
sure to toss it and put in a new one). If your venturi
is to be used outside, the air-intake pipe and cotton-wool
should be protected from rain, otherwise the cotton-wool
will get damp and prevent air getting in. Alternatively
use some green scouring pad, cut so as to fashion a filter.
It doesn't get clogged up when wet like cotton-wool.
Adjustments and Fine Tuning
The tips are adjusted by depth. The tube hanging off
of the venturi intake in the second picture is just an
adjustable air flow device I had laying around from something
else. I think it was made by Marineland for a venturi intake
at the output of a power head. (For standard aquarium use).
The
further in you push the venturi tip, the more restricted
the water becomes, which forces the
water through at higher pressure, so causing a more aggressive
vacuum on the air, but push too far and the vacuum will
have too much air on hand, the water will become a trickle,
and the water pump will begin
to strain.
The further out you pull the venturi tip, the more water
will get through to create a nice current in the pond,
but less air will be drawn in to mix with the water.
Adding more teeth to the venturi tip will allow more
water through, despite the tip being pushed further
into the T-piece. These extra teeth really help the pressurised
water bite into the air being drawn in by the vacuum,
cutting
many
more smaller bubbles, and giving more air intake with
less strain on the pump.
Cutting the Teeth
When I make these
tips out of flexible tubing, I like to use a very sharp
(new) blade for an Exacto Knife, and a triangular jewellers
file. One of the blades that is
my
favorite is one sharpened with leather and a very fine
polishing powder that is for polishing rocks in a tumbler
(final
run). If you don’t desire teeth on
it, the cut from “sharpening” the plastic tube against some sandpaper
gives a good angle and does not need any back side modifications other than removing
the plastic flash.
When I make the notches for the teeth out of a hard-plastic
barb coupler, I generally use a file and sandpaper, and
really take my time so the cuts and angles come out right.
I
believe
that area to be critical to the good formation
of vacuum so that air can be drawn deeper.
Before and After a barb-ended coupler has been fashioned
using the "tooth" design. |
Front Edge of a single-tooth design. Note that the
"barbs" have been sanded off on the tip end of the
coupler to allow the tip to be push-fitted with Teflon
tape. |
Back Edge of the single-tooth design. |
Push-fitted. This is a good position to start with,
giving equal amounts of air and water. |
 |
 |
Plastic can be hard to work with because of the flex
involved. The toothed design works well as long as
you have rigid
enough tubing. If the tubing is not rigid enough the
teeth will fold over. This type of tip works best where
there is no string algae that can reach the tip. The
teeth tend to catch junk easily. I do have one of this
basic
design installed in the outdoor water garden. I use a
filter at the intake of the pump to keep junk out of
it. I took
it apart about 6 weeks ago to see if it was doing ok,
and it looked great. Not plugged at all. If you expect
gunk
to get to the venturi, then just omit the teeth. The
back cut I made was nothing more than using coarse
sandpaper
to get it cut to the correct angle, then using a finer
sandpaper to get the edge formed well. In doing this
you do create plastic junk at the edge. This will have
to be
carefully removed with the Exacto knife.
What I do is lay out a piece of sandpaper on the floor.
I use the concrete floor in our basement. Hold the part
and start working it against the sandpaper. It really
gives you a lot of control that way. Just like with sharpening
a knife, run the leading edge forward. That leaves
the plastic flash behind the leading edge. Easier
to remove that stuff from the back side, and less chance
of damaging the nice sharply defined front edge, which
is the edge that helps break the air/water skin effect.
Choosing Tubing
The tubing that I used for the 3-tooth venturi is “air
riser” tubeing from an aquarium store. These are
used in the back of an aquarium with a bubbler at the bottom
so as to create an air lift. (Water raises with the air,
creating an “air lift”). The most common size
of tubeing is 1”, but I used tubeing that would fit
the part I had on hand. Sometimes the Teflon tape is handy
for fitting parts like these. You will have to add wraps,
press fit, add wraps, press fit, then add more wraps prior
to a final press fitting. Otherwise the part will loosen
because the tef tape compresses.
Take the T with you when
looking for something to fit inside it. That helps a lot.
Make sure to look at individually packaged syringes too.
I buy the kind without the needles on them. Cheaper, and
I would just throw away the needles anyway. Here, they
are usually packaged in a plastic container with removable
end. I have used the outside container if it fits the T.
I like to use rather large tubing for the air intake if
the venturi is to be installed under water. This helps
to keep the fish from knocking it loose. I have used many
ways of attaching the tubing too. I just look at what
I have on hand to see if I can make a reducer for a press
fit. Between tef tape, and all the sizes of “scrap” vinyl
or hard plastic tubeing I have laying around, I can usually
find something. I have used all my old syringe bodies too.
I had to go out and get a couple new ones anyway. The rubber
on the plunger goes bad after a year or so of taking water
samples.
These techniques are nothing special, but it did take some
work and testing (many hours worth) to get to the current
design that I prefer to use. (Basically the design depicted
in the last design in the PDF
document)."
If you have any comments or suggestions about this project
please contact me:
And if you have found these web pages useful and interesting and would like to
make a donation, you may do so using the Donations
Page.
Alternatively if you have questions you would like to address directly to Zik:
Further
Information
I also really like Tim Jansens site which
provides some further information on his venturi pages:
http://www.tim-jansen.com/koi_step-by-step_venturi.htm
 |
You can download and
view/print this whole project at your leisure (size
3Mb, 77 pages). To view Adobe PDF files you will
need to download Adobe Acrobat PDF Reader, click here to
go Adobe's download pages. |
Jims
Pond Blog
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ponding bio-filter and venturi experiments why not
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