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Overflow box
http://byap.backyardmagazines.com/forum/viewtopic.php?f=8&t=3854		 Page 1 of 2
Author:  healingdeva [ Jul 24th, '08, 02:40 ]
Post subject:  Overflow box
We are working on setting up a small indoor system with an aquarium and one grow bed. The water flows...
* from a sump tank up to the aquarium via a pump
* then from the aquarium to the grow bed via an overflow box
* then drains from the grow bed to the sump using a loop siphon

The challenge is the overflow box. We started down this road based on a post by TCLynx...
viewtopic.php?f=45&t=3774&p=137319&hilit=aquarium+system#p137319

Doing some good searching, found the following two configurations that were supposed to work:
http://www.reefbuilders.com/forums/diy- ... -sump.html
http://www.aquarticles.com/articles/man ... nging.html

We've built out both systems with the only exception being the end that draws the water in from the aquarium.

Attachment:
OverflowBox.jpg
OverflowBox.jpg [ 115.21 KiB | Viewed 5644 times ]

Attachment:
OverflowBox 001.jpg
OverflowBox 001.jpg [ 71.57 KiB | Viewed 5643 times ]


The challenge:
I can draw all of the air out and get the water going. However, once the level of the aquarium reaches the top of the intake, it takes in air and the "siphon" action stops. We've added a cap to the top of the "T" on the outside portion because without it, it didn't drain at all.

I've tried several versions as well as a different intake with the same results.

Thoughts, ideas???
Author:  Hex [ Jul 24th, '08, 03:19 ]
Post subject:  Re: Overflow box
Hi HD
It looks ok except the pipe lengths need a tweak. There a few graphics in this thread that may help.
viewtopic.php?f=1&t=1142&st=0&sk=t&sd=a&hilit=syphon&start=15
Author:  Hex [ Jul 24th, '08, 03:41 ]
Post subject:  Re: Overflow box
It looks like the problem lies with the height of the outlet. The tank level will have to be much higher than the intake to create enough "umphh" to fill the pipe full enough to overflow. Here`s a revamp of your photo, the blue line shows the relative water level inside the pipe when the tank level is at the inlet height.

It would pay to make it somewhat higher than shown in the revamped pic as the turbulance from the water falling down into the inlet tube will create air bubbles which could be carried up to the top loop.

Attachments:
OverflowBox revamp.JPG
OverflowBox revamp.JPG [ 65.76 KiB | Viewed 5630 times ]
Author:  TCLynx [ Jul 24th, '08, 04:01 ]
Post subject:  Re: Overflow box
Yes the inlet and outlet need to be roughly balanced in height and should both be a little bit lower than the desired high water mark in the tank.
Author:  TCLynx [ Jul 24th, '08, 04:03 ]
Post subject:  Re: Overflow box
Oh, and you want to avoid it having any ability to siphon since that could draw air into the pipe and defeat the no holes overflow.
Author:  healingdeva [ Jul 24th, '08, 04:11 ]
Post subject:  Re: Overflow box
Several question...

Is the tank water level going to end up at the top of the pipe (my experience so far) or at the bottom?

The outlet should then be below the inlet, but by how much? A pipe's width? I did do a low one similar to what was pictured and it drained the tank to that level, (overflowing the sump AHHHHH!!!!) ;-)

What would prevent the ability to siphon? I believe it is doing that.

I am finding anytime I remove the "plug" from the top of the outlet T, it doesn't work at all.
Author:  healingdeva [ Jul 24th, '08, 04:15 ]
Post subject:  Re: Overflow box
One more question...

The drawing in this thread shows a much "taller" unit.
viewtopic.php?f=1&t=1142&st=0&sk=t&sd=a&hilit=syphon&start=15

What is the benefit of making it taller (Say the distance from the top of the tank to the top of the growbed - in this case 27")?
Author:  healingdeva [ Jul 24th, '08, 04:31 ]
Post subject:  Re: Overflow box
I think I've answered my own questions. We'll let it run for a bit and then I'll post some pics of the "final" version once I know for sure it's going to continue working.

Thanks much!
Author:  TCLynx [ Jul 24th, '08, 04:38 ]
Post subject:  Re: Overflow box
for an indoor system, you may wish some extra sump capacity.

Here is a diagram of the kind of no holes overflows I've been using.

Attachments:
No holes overflow.JPG
No holes overflow.JPG [ 74.25 KiB | Viewed 5624 times ]
Author:  healingdeva [ Jul 24th, '08, 05:00 ]
Post subject:  Re: Overflow box
From my initial design, the key was really to have the outlet slightly below the inlet. The upper part of the "T" is now open as it should be. And, the design worked well enough that I dismantled, keeping it level so I didn't spill water for the picture. Then, put it back together and it went right back to work without me having to clear the air in the "system" again.

Attachments:
OverflowBox 007.jpg
OverflowBox 007.jpg [ 130.16 KiB | Viewed 5615 times ]
Author:  Hex [ Jul 24th, '08, 05:21 ]
Post subject:  Re: Overflow box
Hi HD
Glad you have it all sorted, I`ve used one without any issues.
To automatically remove any air that may get into the top loop I hooked the venturi of a powerhead via a short length of silcon tubing onto a screw-in irrigation fitting at the top of the loop.
In operation the powerhead pulls a small amount of water from the flow in the tube and any air that appears.. goes with it. :wink:
Author:  healingdeva [ Jul 24th, '08, 06:37 ]
Post subject:  Re: Overflow box
We don't have a powerhead with a venturi. We had a catch valve in the top but it allowed air in (yes it was facing the right way ;-) ) so we removed it. Wondering if we put a small tube into the top and the other end in the drain after the outlet if there would be enough suction action to draw any air out of the top?
Author:  TCLynx [ Jul 24th, '08, 06:54 ]
Post subject:  Re: Overflow box
My no holes overflows have been running for some time now with no problems once I got them working right to start. About the only thing I might warn about is that since your inlet starts out horizontal, it might be slightly more likely that you could draw in bubbles compared to an upward facing inlet. Regular maintinance of submerging the parts while re-assembling should take care of air build up that might happen over time.
Author:  Hex [ Jul 24th, '08, 07:19 ]
Post subject:  Re: Overflow box
TCl makes a good point about your horizontal inlet.
I used a vertical pipe with an adapter to make the top section larger, it also gave the option of using a chunk of coarse sponge to filter out large objects.. limited usefulness with AP as you want the solids to go through.
The venturi was just a safety precaution and isn`t essential. Another option may be to use 2 units..its very unlikely both will get an airlock at the same time.
Author:  healingdeva [ Jul 24th, '08, 07:50 ]
Post subject:  Re: Overflow box
The goal is to make the inlet "fry-proof" as the point of this tank is for breeding. It seems to be working though the top level fluctuates a bit. Is that normal to have some variation on the upper water line?

One of the configurations I did had an upward facing inlet, however, it drew in air faster than the horizontal one. Though, it was likely due to the level of the "T" outlet. That was a key factor in getting this running.
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