Siphon u-tube question

[jarrodaden]

Shortly after I posted the video at this thread

http://www.houstonfishbox.com/vforum...iphon-overflow.

I received a question from another box'r asking how much flow a 1-inch siphon utube can handle. I already had all my stuff in the driveway, so I ran a test. Here is video showing the test.

http://www.youtube.com/watch?v=_tNZysyNIL0

Here is the answer.

When a siphon is setup, the siphon will seek a balance (equal water height) on each side of the siphon. When the water level in higher in the aquarium, water will be pushed to the box on the outside of the tank. The higher the water level in the aquarium, the faster the water will flow.

Based on my test, here are the results.

0.3" -> 135 gph; 0.6" -> 199 gph; 1.0" -> 258 gph; 2.2" -> 423 gph

Here is the rating curve

1inchsiphonratingcurve.jpg

I would say that you can reasonably expect to move about 500 gph per siphon tube depending on how much head (water height) difference your aquarium and overflow box can tolerate.

[snookfish]

nice info. helps alot for ppl like me looking for exact answers to these kids of questions

[mark razmandi]

thats very interesting but ive always been told a 1inch can handle 1200gph?

[CichlidFan]

I was told by Andy at fishland, approx 450 to 600....depending on height of the stand and the size of the tank.....average will normally be close to or just over 500 GPH....

CF

[jarrodaden]

Andy's range is reasonable based upon my test. That said, height of the stand and size of the tank aren't what drive the flow rate. It is the difference in water surface height between the overflow box inside the aquarium and the other box hanging outside the aquarium that will "push" the water through the u-tube. The bigger the difference, the higher the flow.

Watch the video and you will see what I mean.

The 1,200 gph number might have come from somebody's real life experience using a pump rated for 1,200 gph with a single u-tube. This is actually possible even though the u-tube was probably moving something closer to 600 gph, but I am saving that topic for my next video....

If it helps convince you, I am a Civil Engineer with a specialty in hydraulics and hydrology.

[specialone0812]

Bernoulli equation right Jarrod? pressure, velocity, head height make the difference.
tony

[jarrodaden]

Unfortunately, with the equations which would be applicable to aquarium type problem there are many constants and coefficients which may apply. In this case, there are entrance and exit losses in addition to friction losses. Rather than trying to guess the appropriate ones, it is easier (and perhaps more accurate) to setup a mini hydraulics lab in the driveway.

The Bernoulli equation is definitely applicable in this discussion.

[Chef]

Jarrod that's a very thorough explaination. How do you contend with air bubbles being trapped at the apex of the U?

[jarrodaden]

As I said in the video, I am in the process of setting a wet / dry up for the first time. I haven't ever run the complete system before.

That said, from what I have read and been told this problem occurs when the u-tube isn't adequately submerged. Some say that rapid flow through the tube will clear the bubbles.

[wesleydnunder]

As I said in the video, I am in the process of setting a wet / dry up for the first time. I haven't ever run the complete system before.

That said, from what I have read and been told this problem occurs when the u-tube isn't adequately submerged. Some say that rapid flow through the tube will clear the bubbles.

It should, similar to the way it clears them from the intake tube of a canister.

Mark

[myjohnson]

In some cases it will not. If the flow is too weak for example.

I have seen people drill a hole on the top of their u-tupe and glue an air line to it.

That way they can suck the air out as needed and plug the air line up.

[specialone0812]

i think that happen whenever the flow rate of the pump is weaker than the flow rate of the U-tubes, then air will get in (in some cases, people put their air-pump, or powerhead tube close to overflow box that make bubbles fall to the box inside the tank, and then to the U-tube).
if there is air in the U-tube, rapid and strong flow to the U-tube will push all the air away.
its my experiencet, put your return hose from the pump back to the tank as straight as possible to reduce friction loss. also use a pump with the flow rate a little stronger than the flow rate of your U-tubes . i used an overflow box with single U-tube ( 500gph approximately) and an Mag 5(500gph), seemed to be adequate, but i got air in the U-tube sometimes, i straightened the return hose, changed to Mag 7, and i have not got any problem with air in the U-tube.
just my 2 cents.

[jarrodaden]

It should, similar to the way it clears them from the intake tube of a canister.

Mark

It works a little differently with a cannister. A cannister typical has flow entering the bottom and exiting the top. Bubbles natrually find their way to the top. With the u-tube, the bubble travel up (to the top of the tube) and have nowhere to go unless enough water is moving to push them down and out the other side.