syphon U- tubes

[sjm817]

I ran one for ~ 4 years with never a single issue. I have a friend who has ran one for ~ 6 years. No problem. I've seen plenty of posts on RC of people with similar posts. If it is a well designed unit and set up properly, it will never accumulate air. It will run indefinitely without an issue. There is no need to add anything to fix a problem that isn't there.

 

[oldsaltman]

<a href=showthread.php?s=&postid=14466083#post14466083 target=_blank>Originally posted</a> by sjm817
I ran one for ~ 4 years with never a single issue. I have a friend who has ran one for ~ 6 years. No problem. I've seen plenty of posts on RC of people with similar posts. If it is a well designed unit and set up properly, it will never accumulate air. It will run indefinitely without an issue. There is no need to add anything to fix a problem that isn't there.

That is great, and I am glad that is works for you! I just don't remember a lot of post about how happy everyone was with their "U" tubes.

 

[GunnerO]

Ah, Increasing flow... to fix the air bubble problem. I've had constant problems with air getting into the U-tube.

Can you increase the flow but lowering the collection box inside the tank before the U-tube sucks it up? Thanks.

 

[jus10kase]

It`d be nice if someone explained HOW to increase flow.

 

[oldsaltman]

<a href=showthread.php?s=&postid=14467371#post14467371 target=_blank>Originally posted</a> by jus10kase
It`d be nice if someone explained HOW to increase flow.

I guess you just keep buying bigger pumps until the "U" tube works.

 

[Toddrtrex]

<a href=showthread.php?s=&postid=14467446#post14467446 target=_blank>Originally posted</a> by oldsaltman
I guess you just keep buying bigger pumps until the "U" tube works.

Just start off with a properly sized pump for the U-tube to begin with and won't have the issue.

<a href=showthread.php?s=&postid=14467371#post14467371 target=_blank>Originally posted</a> by jus10kase
It`d be nice if someone explained HOW to increase flow.

There are two ways, smaller diameter U-tube, or more flow from the return pump. If you have a ball valve on the return side, open it more.

Lower/raising the box (( the one inside the tank )) will just effect the level of the water inside the tank, and won't effect the flow.

 

[sjm817]

Its amazing how something so simple can be so misunderstood.

U Tubes work off a very simple siphon principle. Nothing new here. The problem is water flowing over a weir carries bubbles with it. If there isn't adequate flow through the U Tube, they can accumulate in the apex. Have enough flow, they dont.

There are other factors, Not all U Tube overflows are created equal. Some are designed very well, some are not. Because of the design differences, some are more susceptible to air accumulation than others. A U Tube overflow that would require an external vacuum pump to remove air would be a very poor unit.

How much flow is needed? The typical overflow with a 1" U Tube needs about 200 GPH minimum to keep bubbles pushed through. Not a ton of flow. A Mag3 can do it with typical head. An overflow with a smaller U Tube like 3/4" will need less.

How to increase flow? If the pump is too small, use a bigger one. Often, people use inadequate pluming. Just using a better plumbing setup will often fix the issue.

Again, use decent equipment and set it up properly and it works as designed. No different than anything else. There is always the option of a work around fix instead, but its not difficult to do it the right to begin with.

 

[sjm817]

<a href=showthread.php?s=&postid=14467169#post14467169 target=_blank>Originally posted</a> by GunnerO
Ah, Increasing flow... to fix the air bubble problem. I've had constant problems with air getting into the U-tube.

Can you increase the flow but lowering the collection box inside the tank before the U-tube sucks it up? Thanks.

Actually raising the box up helps some. The height of the box has no effect on GPH. That is controlled by the return pump.

A siphon works by the difference between the high side and the low side of the levels. In an aquarium overflow, that is the skimmer box and the drain box. The greater the distance between the high side and low side, the stronger the siphon. This is what I was meant by not all overflows are created equal. Some such as the Lifereef pay better attention to this than others and is why they work so well.

To adjust your overflow, raise the skimmer box up if you can. On the drain side, sometimes depending on the setup, you can tweak that a bit. If it uses a standpipe, have it high enough to keep the U Tube submerged, but no higher.

If you need more flow, how is your pump plumbed? The type and diameter of the tubing, hose barbs, elbows, etc all have an effect.

 

[jbird69]

If your water is entering your overflow box with lots of turbulance, you will get lots of bubbles passing thru your u tubes. As u tubes build up with algae the flow will become restricted. If you get good amounts of hair algae in the u tubes, they can start to snag bubbles. This combination can potentially lead to your DT slowly overflowing. The teeth, or critter stop you put on the rim of your box can create turbulence. Its a good idea to do something to smooth out the flow into your overflow box if its turbulent or splashy. And its really important to not let too much algae build up in the u tubes. I keep meaning to build a shade for mine to protect it fro my MH lighting. this will make a huge difference in how often you need to deucsh out your u tubes.
A correctly designed external overflow with utubes is foolproof, but it is definitly not mainanance free.

 

[sjm817]

Good points. I had a little shade over mine to keep the (T5) light out. I would clean out the U Tube every few months. It would get brown slime in it. Also on the turbulence going over the weir. A smooth toothless weir would work best. Still, bubbles will get in the U Tube. Adequate flow will keep them from accumulating.

Here is an old pic I found from 2005. Nice and clean!