Air in U-tube overflow

[kelipalmer]

Hey guys,
We've had a 100 gal setup for over ten years that utilizes an external overflow box with a U-tube. A few months ago, it began getting significant air bubbles in it. Occasionally, it gets enough air trapped that it breaks the siphon.
To my knowledge, nothing has changed in our system, but clearly, something has happened.
Of course, we're getting ready to go on vacation soon and I am nervous since we can't check it every day.
I need ideas of what might be causing the problem and what we can try to fix it (yes, I know... we should have gotten a drilled tank!)
Thanks

 

[researcherresort]

To the best of my knowledge, our system has not undergone any changes; yet, it is obvious that something has transpired. Naturally, we are getting ready to leave on vacation very soon, and since we won't be able to check it every day while we're gone, it's making me concerned.

 

[melev]

I would clean it, as well as the inner and outer boxes. Usually the air comes from the water pouring into the inner box, and the U-tube sucks those in a few at a time until there are too many. Perhaps the tube wasn't pressed down far enough, or the inner box has dropped a little lower over time and needs to be raised up again.