overflow tube help?

[corbett_n]

My overflow u-tube keeps getting an air bubble stuck in it, which slows down the syphon rate. Water falls into my external overflow box creating bubbles that get sucked into the tube and accumulate I guess into a bigger bubble. I noticed one side of the tube is longer than the other, which side goes in the tank side and which goes into the box on the back? What can I do?

[stingythingy45]

Sounds like you don't have enough flow to wash the bubbles through the tube.What are you using for a return pump and what's the overflow type?Explain your system a little...

[RedDmon]

Reverse the U-Tube.
Drop your intake to allow more water in.

[gws76]

stingythingy45 is exactly right on this one. If you have bubbles accumulating at the apex of your U-tube you're not getting enough flow.

[corbett_n]

I have a Mag 5 returning the water from the sump to a 30g tank. I have a valve on my line from the external box. What if I closed the valve a little would that do anything? I will try and lower my box some when I get home.

[corbett_n]

Is the longer part of the tube suppose to be in the front box or the back box?

[cdbias2]

In the back normally because that is where the water level is lower.

[gws76]

Not sure on the U-tube on whether the long end goes in the outside overflow box or the inside. Mine is the same length either way. A mag 5 should be plenty of return pump for that size tank. If you open your ball valve on your drain line it should speed up the flow thru the U-tube, but then you would have to crank the flow up on your mag 5 return pump so you don't overflow your sump.

[corbett_n]

I have both of them wide open

[gws76]

What size pvc pipe or hose do you have on your return and drain line?

[corbett_n]

I think the drain line is 1.25" and the return line is smaller but I can't remember what. It is hooked to a Mag5 so what ever that is

[stingythingy45]

Sounds like your Mag 5 is seriously whimpy or has something plugging the return line.You should be watching bubbles blast through that U tube like stars in warp speed.

[gws76]

Since it's a mag5 it should be 500 gph return, but your head loss will take some of the gph down a little. I'm currently using a little giant that starts out as 500 gph, but after it returns 3.5 ft. up to the tank, I end up with somewhere around 400 to 450 gph. Which has been plenty of return for my tank, meaning I don't end up with air bubbles building up in my u-tube.
Your drain line is plenty big enough.
I would try RedDmon's solve for this one, maybe it will work.
You should have plenty of return gallons, "scratching my head".

[stingythingy45]

I think you need to pull the return and see how much flow you have at the head distance.And check to see maybe if something got sucked into that pump.I have a 800 GPH U tube overflow that I'm pushing about 450-500 GPH through and bubbles blast through the tube.

[reefnut1]

Everyone is correct more flow will get rid of the bubble.
If you do not desire to increase your flow you can take an airline and attach it to a Maxi Jet air intake and run the other end of the line inside your tube to the top and it will suck the air out as the bubble forms.
I travel regularly and leave my tank unattended for 3 -4 days at a time, this insures that I will not loose the suction in the u tube.

[shleprock30]

When you first start the syphon do you have an air bubble or does it run for a while with no air bubble and then just start to build up.

When I start mine I like to let the return pump fill the tank higher then I normally run it so there is a good strong suction to start out with, otherwise a bubble can form and you will never get rid of it.

I had a U-Tube a long while ago that always seemed to get a bubble, I finally replaced it and all was well. For whatever reason it just never flowed smooth, the only thing I changed was the tube and I did not ever have another problem with that Overflow.

Rick

[asm481]

Dropping the inner box on the overflow will do nothing to stop the bubble forming. The tank level will lower and stay there with the same flow. You must be having to little flow, that is all there is to it. What size tubing is on your return? Might want to upsize the tubing to increase flow. I don't know the Mag5 but the directions on a mag12 say double the thread size for maximum flow. Yes that means 1 1/2 inch for a Mag12, check the Danner website if you don't believe me. I run a double tube overflow and with a lower flow I get bubbles too. Another option might be to get a smaller diameter U tube. If yours is 1 1/4 as most are try to get a 1 inch.

[corbett_n]

I lowered the box inside and for now it has worked. It shot the big bubble right through the tube. i will look into getting a bigger return line though. thanks for everyones help.

[RedDmon]

<a href=showthread.php?s=&postid=12247461#post12247461 target=_blank>Originally posted</a> by asm481
Dropping the inner box on the overflow will do nothing to stop the bubble forming.

REALLY? Seems to have done the job in this case. Worked on my set up. Start with the simple things then get into the more complex, and or expensive solutions.

[asm481]

<a href=showthread.php?s=&postid=12251848#post12251848 target=_blank>Originally posted</a> by RedDmon
REALLY? Seems to have done the job in this case. Worked on my set up. Start with the simple things then get into the more complex, and or expensive solutions.

Temporary fix. If bubbles in the u-tube are forming cause of to low flow, dropping the inner box will increase flow for a short bit and flush any bubbles out but they will build again in a short while.

[cdbias2]

Lowering the box creates larger holes through the teeth of the box for the water to flow through. It will lessen the bubbles as you have already noticed. As long as you dont lower your DT water level too much you'll be fine.

[stingythingy45]

Huh.....why would dropping the inner box do anything?All that does is lower the water level in the tank.Does nothing to cause a stronger siphon or flow.I would thing raising it would do a little more.It would create a greater distance between the level in the tank and the outer overflow box level.

[corbett_n]

It seems like it creates less bubbles falling into the box, which made less bubbles going through the u-tube. Just my observation