External overflow U tube loosing siphon

For about 2 months I have been trying to figure out why my u tube keeps loosing its siphon. Actually it never has completly lost it(see video). I have tried everything I can think of. Cleaning it and the overflow box, adjusting the return pump flow, adjusting the height of the overflow box, removing the overflow box filter... I cant figure it out! Any ideas?

 

When I slow my return pump down too much air bubbles get trapped. I saw it one day almost loose siphon because of that. Once I added a little more flow it pushed the air back out.

 

You can put a small one way valve into the apex of the utube and run a line to a small dosing pump. It will keep pulling the air out and keep all the bubbles gone. Put the return line right into the overflow. I've seen people do this on YouTube clips and it works well. I'm doing something similar for my soon to arrive CPR overflow that doesn't use a utube but has the check valve built in. Good luck.

 

I have a Tom's Aqualifter on my u tube. It does a great job of keeping the siphon going and even restarts it after a power outage. I think the even come with the CPR deluxe units. Very cheap only about $14-$15.

 

Tho I can't see the video, (prob my pc)
I think this is the best solution.

Or you may want to stop by your LFS and see if they have a u tube with a smaller diameter. The smaller diameter u tube can have the water flow faster, which will simply suck the bubbles out. (if that is the problem, again, I can't see the vid)

I'm NOT a fan of the overflows that rely on a toms aqualifter (or other) pumps to keep siphon. The design of using a u tube is that it WILL (if in a proper set up) automatically restart on it's own.

Keep the flow fast enought to push ALL bubbles thru and you won't have an issue.

 

BTW FatBastad it's not your PC I can't see the video either.

 

the video isn't working anymore....i'm assuming you have a sump that you're porting that water to....I dumped my manufactured overflow and built me one of these...
Super Sucking Siphon - EvilWiki

It's the best overflow without drilling that you can have and I also did a little mod to it by getting rid of the priming line. Since i have a water changer all you do is stick the tube down the breather and let it suck all the air until it starts pulling water and you're done!