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How do you keep overflow tubes from filling with air

HOB overflow? Egads Sergio! :D

Its been a while, but I think the big issue with them is that they're quite fickle as far as flow rate, too slow and the tubes nearly drain the tank side container and the long drop of water causes bubbles and they just naturally get sucked in, too fast and strangely a similar thing happens. You could always hook up the siphon hole(s) to an aqualifter or something and simply put that on a timer for a few minutes every day to suck out the air (and water). Of course knowing now what I did then if I wanted to rely on that technology I'd definitely hook my return pump to a float switch, just in case the siphon pipes catastrophically fail.
 
I had the same issue with a single HOB box, went with a lower GPH pump and improved quite a bit but every now and then I had to check for air bubble; at some point raised the U tube with something under it and seemed the extra height helped a bit.
When I changed tank decided it was too much trouble so decided to make it easier for the new owner, drilled the tank top center.
 
You can glue a nipple that accepts airline to the overflow tube and hook it up to the venturi of a small powerhead, that way the air is getting sucked out at all times.
 
tuberider said:
You can glue a nipple that accepts airline to the overflow tube and hook it up to the venturi of a small powerhead, that way the air is getting sucked out at all times.
Click to expand...

+1
Works like a charm.
I had one for 5 years like that with very few problems.
 
I will never use a HOB overflow again. When my display was a 10g with a 10g sump, I used one of these. I had 2 floods, which was 2 too many!

I paid good money for a HOB too (off eBay, back when I was stupid(er)). What a waste!

I found that faster water flow was better, because it sucked bubbles down. I like the power-hear/venturi idea. But ugh, never again with HOB.

V
 
I should be more clear on the issue at hand. One of the overflow u-tubes will suck up air bubbles and in about 3 days time it will have quite a bit of air built up inside and looks to be siphoning at 50% yet the other u-tube is fine. I removed one tube a week ago and the remaining tube seems fine with no air bubble build up. I'll keep on eye on it for a good while to see if any more problems.
 
2 tubes not same elevation so flow is different
or
more bubbles entering one tube than the other
or
both?
or
crack in tube sucking air in
or
something else!

pic of tubes into overflow would be nice. Or a movie of the bubbles in the overflow/turbulence.
 
2 tubes same elavation , one seems to get more air bubbles (I can change air bubble build up from one tube to the other by changing angle on over flow box) , neither one is cracked. When both tubes used there seems to be less force going thru them.....if one tube removed there is more force going thru the single tube and no bubbles appear.
 
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