DIY Venturi

[F.H.Chan]

Hello Folks!

I've been trying to build my own DIY venturi valve out of 6/8" PVC tubing.
As far as I understand, where
the water inlet is, the hole will narrow down to about 2/8" dia in a very
short distance like 6/8" lgh. At the
bottle neck of 2/8" dia, it wll run around 3/8" straight before enlarging
back to 6/8" via a distance of 1.25".
An air tube is inserted into the 2/8" dia straight section.

I tested it in an unused fish tank filled with fresh water and the bubbles
are rather big. Not as fine as
those of ready made skimmer. Does anyone knows why?

Is there a difference in testing it in sal****er against freshwater?

Does anyone have any advice in making a venturi valve?

Thanks!

Regards,
Mark

[Comatose]

On Wed, 15 Mar 2006 11:33:46 +0800, "F.H.Chan" >
wrote:

>Hello Folks!
>
>I've been trying to build my own DIY venturi valve out of 6/8" PVC tubing.
>As far as I understand, where
>the water inlet is, the hole will narrow down to about 2/8" dia in a very
>short distance like 6/8" lgh. At the
>bottle neck of 2/8" dia, it wll run around 3/8" straight before enlarging
>back to 6/8" via a distance of 1.25".
>An air tube is inserted into the 2/8" dia straight section.
>
>I tested it in an unused fish tank filled with fresh water and the bubbles
>are rather big. Not as fine as
>those of ready made skimmer. Does anyone knows why?
>
>Is there a difference in testing it in sal****er against freshwater?
>
>Does anyone have any advice in making a venturi valve?
>
>Thanks!
>
>Regards,
>Mark
>

Yes, there is a big difference testing between salt and fresh water,
if your testing for if something just works you test in plain water,
if you want to test anything with air injection you need to test in
sal****er to make sure your getting the effect you want out of it,
and to be able to make adjustments.

try adding salt to the water and you will see a big difference in the
bubbles coming from your venturi, also there is a slight breakin
period for any type of skimmer.


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[F.H.Chan]

Thank you! Thank you!

Very true indeed. All the prototype venturi I made works after testing it
salt water.. Since each has a difference in design,
some of them worked rather well.

Type : Comment
-------------------------------------------
Venturi with direct air in-take : High volume of bubbles but not as fine.

Venturi using indirect in-take : Superb volume of air with finer bubbles.

Venturi using very small bottle neck : Significant drop in pressure with
good fine bubbles.

Venturi with 2 needle hole in-take : Fine bubbles but small volume

Notes:
-------
Venturi with direct air in-take : Typical venturi found in most skimmer.
Mine was from a 6/8" dia
with a 3/8" bottle neck which the ait intake is located.

Venturi using indirect in-take : Dia from 6/8" to 3/8". The wall of the 6/8"
was fitted with a
2mm single hole in-take. While the walls of the 3/8" dia bottle neck was
drilled with 0.8mm
tiny holes as many as 15 holes.

Venturi using very small bottle neck : This is very similar to typical for
sale venturi.
Small bottle neck of 2/8" will allow small powered pumps to drive. However,
if your
skimmer is like mine of 24" tall, the back pressure maybe too great to
perform efficiently.

Venturi with 2 needle hole in-take : The air in-take is only 2 number of
0.8mm holes.
This results in nice fine bubbles but at a much lower volume of it. Dia is
from 6/8" to
3/8" as well.

Regards,
Mark


<Comatose> wrote in message
...
> On Wed, 15 Mar 2006 11:33:46 +0800, "F.H.Chan" >
> wrote:

>
> Yes, there is a big difference testing between salt and fresh water,
> if your testing for if something just works you test in plain water,
> if you want to test anything with air injection you need to test in
> sal****er to make sure your getting the effect you want out of it,
> and to be able to make adjustments.
>
> try adding salt to the water and you will see a big difference in the
> bubbles coming from your venturi, also there is a slight breakin
> period for any type of skimmer.
>