overflow gets air bubbles in U -tube?

[ser_renely]

I have been trying to figure out why my U-tube has been filling up with air over a days period? I don't get why it does and it slows down the amount of water going into my sump. My sump level seems to change and with no leaks, and salinity being the same I figured the levels would stay constant....not true. So either water is being stolen or the flow rate is changing somewhere.

I must be missing something very simple. Ideas?

[Curve]

It sounds like your overflow is rated for alot more than your return pump can do. I ran into this problem. I put an eshopps overflow that was capable of 1000 gph with a return pump that would only do like 600 gph at the head loss. I kept getting these air bubbles in one of the utubes until it would just lose siphon and run off of one u tube. I ended up downsizing my overflow to one rated for 600 gph and matched it with the return pump and I have not had any more problems. To make a long story short, it sounds like your pump is way smaller than your overflow so it does not need as much water. In turn it is causing the air bubbles in the u tube. What exactly are you using for an overflow and for a pump. Also how much head loss do you have???

[mg426]

I would agree that the above answer is a good thing to look at.

[Dave413]

I also agree with the above. Faster flow through the u-tube will push the micro bubbles out so that it does not form a large one that will break the siphon.

[sdtopgun]

get an aqualifter to suck out the air in the u tube

[jdieck]

<a href=showthread.php?s=&postid=13891648#post13891648 target=_blank>Originally posted</a> by sdtopgun
get an aqualifter to suck out the air in the u tube
http://reefcentral.com/gallery/data/586/18470Overflow_w_lifter.jpg

[RicksReefs]

yup, all you need to do is match the return pump flow closer to what the max amount of flow that the overflow tube can handle.

[yardartist]

This happened to my set up at first. I purchased a 'complete' system from craig's list. Same small pump to large diameter siphon tube issue. I tilted the siphon tube to be angled so the outflow end was raised very slightly and the inflow side deeper in the overflow box. This allowed the micro bubbles to flow out before grouping together. The air accumulation in the top of the tube dropped to zero. Richard

[thecoralreefer]

That would work or you could slide a reducer onto the pipe inside the box
This can be adjusted in size and you will control the flow by downsizing the tube

[ser_renely]

how do I figure out what my overflow is rated for?


Thanks for all the input guys. :)

[Curve]

What size is the u tube. 1 1 1/8" u tube is rated for about 600 gph. 2 are rated for 1200 gph.

[ser_renely]

Its a 1-1/4" OD U-Tube, the one from foster smith...

http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=4024

Thanks for the help :)

[Curve]

I may be wrong b/c I now have myself think the 1 1/4 u tube is what does the 600 gph and the 1 1/8 does about 500gph.

[ser_renely]

ok should be a good enough baseline to work off of. I think I only am putting out 350gph after loss with my pump.

[Curve]

definitely need to downsize on the u tube or upsize the pump.