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 Post subject: no holes overflows
PostPosted: Sep 15th, '12, 10:41 
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Ozinbrasil, it seems like the jet priming design would have the issue that a large proportion of the inflow water would directly flow out of the overflow, which would allow the water in the vessel to stagnate rather than be cycled.

I wonder if a Venturi vacuum might be a way to suck the air out of a no-holes overflow. I've never constructed one though.


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 Post subject: Re: no holes overflows
PostPosted: Oct 11th, '12, 16:03 
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Hi

Natetrue wrote:
I wonder if a Venturi vacuum might be a way to suck the air out of a no-holes overflow. I've never constructed one though.


This is probably a long shot and defying the laws of physics, but what about this - see attached diagram.

The diagram shows the very top of the NHO.

A T-Piece is used to get any air above the normal line of the NHO pipe.

An air tube is connected from the end piece to the venturi pipe that is connected to the L-piece.

I doubt whether there is enough flow pressure to suck the air back and force it to go with the flow of water. If there was not enough flow in the first place to move the air bubble through the NHO pipe in the first place.

Also, when priming by sucking the non-return valve you would probably have to squeeze the tube at the venturi end to stop water from be sucked back through.


Cheers,

Mon


Attachments:
NHO - air - venturi.PNG
NHO - air - venturi.PNG [ 24.14 KiB | Viewed 4189 times ]

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 Post subject: Re: no holes overflows
PostPosted: Oct 11th, '12, 16:32 
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Hi,

Forgot to mention, even without the venturi setup, the T-Piece at the top should have the following benefits.

Assuming the NHO is primed to near the top of the end piece above the T-Piece, any air bubbles will get trapped here and should be above the normal pipe line of the NHO. Thus, there will be a larger amount of air trapped before it stops working.

I have been thinking of ways of indicating when there is air trapped in this T-piece pipe. I've come up with the following:

Make the pipe connecting to the T-piece a clear one. You can then see the level of the water. If there is air trapped then the water level will go down. You can make this even more obvious by placing some kind of bright coloured floating ball to give a better visual indication of the water level.

However, being a clear pipe this may mean that algae could build up and visibility reduced. I suppose you could tape up the clear tube to above the water line, but enough to still see the floating ball thingy.

Cheers,

Mon

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 Post subject: Re: no holes overflows
PostPosted: Oct 11th, '12, 17:04 
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Guys I just came up with an idea.

Air bubbles are always going to rise in water hense why the upside down U does not stay primed.

So I was thinking what if inside the aquairium there is already an upside down U that is ofcourse under water at all times. This way the air will end up building up in this underwater U bend. Then every now and then a valve is opened under water that just lets the air escape to the surface of the aquarium. This valve could have a water prrof servo so it can be automatic.

It's basically an underwater ait trap that periodically lets the air out before the air makes it to the water bridge.

Would it work?

Edit: Actually looks like some already are doing this.


Last edited by MacGyver on Oct 11th, '12, 17:13, edited 1 time in total.

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 Post subject: Re: no holes overflows
PostPosted: Oct 11th, '12, 17:09 
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Hi,

This is what I was talking about with the level indicator.

There needs to be a way stop the ball from getting beyond the T-piece.

Cheers,

Mon


Attachments:
NHO - air - level indicator.PNG
NHO - air - level indicator.PNG [ 16.76 KiB | Viewed 4181 times ]

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 Post subject: Re: no holes overflows
PostPosted: Oct 11th, '12, 17:40 
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Does this not work?

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water bridge1.JPG
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 Post subject: Re: no holes overflows
PostPosted: Oct 11th, '12, 18:13 
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MacGyver

That hole is basically the venturi in the NHO design drawn up by TCLynx at the following post:


viewtopic.php?f=8&t=4086#p147671

Image

I suspect that it will catch some of the bubbles but some will still get pass it.

Cheers,

Mon

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 Post subject: Re: no holes overflows
PostPosted: Oct 11th, '12, 18:25 
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Thanks Mon.

I was thinking of extending the down section of the U to help prevent bubbles.

As you said though it still might not be effective.

See TCLynx diagram modified so there is less chance of bubbles making it to the bridge.

Attachment:
water bridge mod.JPG
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 Post subject: Re: no holes overflows
PostPosted: Oct 11th, '12, 18:33 
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Hi,

I've thought of another option - have the air tube from the non-return valve inside the NHO itself - see attached picture.

This means that you do not have to drill a hole for the air tube. However, there may be difficulties in assembling the NHO and getting the air tube in it. The air tube will need to be secured so that it cannot come loose. If it is secured to the end-piece by its end then you need to drill holes in the air tube.

Cheers,

Mon


Attachments:
NHO - air - tube inside.PNG
NHO - air - tube inside.PNG [ 33.61 KiB | Viewed 4195 times ]

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 Post subject: Re: no holes overflows
PostPosted: Oct 11th, '12, 18:36 
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MacGyver wrote:
Thanks Mon.

I was thinking of extending the down section of the U to help prevent bubbles.

As you said though it still might not be effective.

See TCLynx diagram modified so there is less chance of bubbles making it to the bridge.

Attachment:
water bridge mod.JPG



I was thinking that too, but I think it will depend on the flow rate. If it is high then the bubbles will be dragged along. But then again, if the flow rate is high then why is the bubbles staying at the top of the NHO?

I don't know - since I haven't even got an AP setup let alone an NHO. This is just all theory to/from me.

Cheers,

Mon

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 Post subject: Re: no holes overflows
PostPosted: Apr 25th, '13, 05:51 
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What about a one way air valve that lets air out at the top and a slow drip line in at the top of the system? Just a thought on keeping it primed.


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 Post subject: Re: no holes overflows
PostPosted: Apr 30th, '13, 02:10 
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Thankyou to Rupert who referred me this thread.
My original post -
viewtopic.php?f=1&t=16341


This siphon pic here is mainly for a fast cheap construction, using only one 90' elbow, since that is one of the more expensive parts. . No expensive valves, no cheap valves.
People can improve on, it when they want to spend more on parts. (Re: check link on the line above.)
I wanted it to be inexpensive and easy to check and remove air.



The clear flexible tube from the box, (a box or whatever other shape people use) needs to be wide enough to let water go down as air rises in it.


This link is another type of simple "Bridge siphon" that I located on the internet that has a good description. .
http://www.youtube.com/watch?v=4IVc7oq29Uw
This youtube video shows how to tap in or attach a small tube to the top of siphon.
------------------------------------
.


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siphon68 btest.jpg
siphon68 btest.jpg [ 44.81 KiB | Viewed 3652 times ]

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 Post subject: Re: no holes overflows
PostPosted: Apr 30th, '13, 03:36 
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This video is actually from one of our highest contributing members, Rob. If you have not seen the rest of his fantastic work, please do a forum search for "Rob's geodesic dome"......it is mind blowing.

Edit: and the link viewtopic.php?t=8898


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 Post subject: Re: no holes overflows
PostPosted: Jun 13th, '16, 11:05 
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Hi all!

I wonder if this thread is still alive or revivable! :D

Did by any chance anyone try to connect a small airhose (1/8"or even smaller) to the top of the inverted U and connect this to a venturi in the ST to FT pump line?
I would suspect that there would be enough low pressure to suck all the air out of the NHO!

On this thread I only saw the version where the air-line goes into the outflow leg of the NHO itself, but none that pulls the air off to a stronger low pressure area...

Either close to the pump where water flow speed is highest or close to the exit at the FT (depending on layout of the pipe work)

If you do NOT like the idea of some of the water being pulled out of the NHO, one could place a small check-valve into the line - something with a floating ball design - floating in water but not in air - as soon as water gets sucked into the airline it would plug the same.

A similar valve at the venturi end could prevent air getting drawn in when the pump stops to work.

On the other hand if the low pressure from the venturi in the water line is strong enough this could also re-prime the NHO after air got back-sucked into it - as long the NHO inlet and outlet remain under water at all times.....

This would be a automatic primer as soon as the pump flows water and it really should not matter if it gets air into it when the pump stops....

The REAL question is - IF the venturi can produce a low enough pressure to pull the water into the NHO!!

Cheers,

thjakits 8)

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