help on overflows...

[fishfriends05]

My in-laws are currently running a CPR overflow. The fitting in the top of the overflow that you hook the airline to, that draws the air out of the overflow keeps getting clogged. So the overflow slowly accumulates air bubbles in the top and slows the siphon almost to a complete stop. I've tried putting screens and filters in the inlet to try and prevent clogging, but the filter material slows the flow down to much and the screen doesn't work either, it just delays it clogging. So I am wondering if this is a common problem with the CPR's or if I am doing something wrong. I don't think I am doing it wrong because when it's not clogged it works great. On my own tanks I've built my own overflow. (which I got the plans on 'how to' from this site.) the thing works flawless and silent. The only problem is, that it is a small eyesore which my in-laws don't want. So is there a way to prevent clogging or is there a better model out there? Any advice would be great.

 

[yaksplat]

How long is it taking to clog?

 

[fishfriends05]

It takes a couple of weeks but it's never gone longer than three weeks.

 

[yaksplat]

mine's been fine for well over 2 months now. I do see occasional growth in the silicone tubing that I have attached. I just squish the tube between my fingers to loosen it up and it flows right down the tube into the sump. At the end of the tube is the venturi inlet of a maxijet 1200.

 

[fishfriends05]

The airline runs into the exact same powerhead. (maxi 1200) To unclogg it I disconnect the tube from the powerhead and blow through it and it usually uncloggs it. Not a big deal except when it happens when they are out of town. Luckily it only overflowed a little. maybe a half gallon or so. Would drilling the center of the fitting in the overflow a little larger help out the problem?