Air in U Tubes

[kvv711]

I was wondering if anyone ever had this experience. I have an outside overflow that works fine, but it seems that every once in awhilw, the u tube seems to get air trappen in it, and the flow decreases. I added a second U tube, but it still happens.
I checked the tubes for leaks (both air tight), and I have no bubbles in the tank. How could these tubes be getting air into them?
Thanks

 

[debbie g]

Mine do the same thing. I don't know why it happens, but I know how to fix it. In case you don't already know...you take a flexible piece of hose that will fit into your u-tube, stick it in a little farther past the bend. Suck the air out and crimp the flexible tube to keep any air out while you pull the flex-tube out of the u-tube. HTH

 

[kvv711]

this happens arter all the air is out, and it has been running for a few hours/days!

 

[razoreqx]

Something to check for. ....
Low flow. If your flow rate is less than the overflow is rated for it will create air bubbles in the catch which build up in the UTube over time. Increase the volume of water and it should stop.

 

[mburnickas]

The would help but if the sump loses water faster, hence water level drops too fast, then you are casuing more problems.

 

[jeepboy]

Razorx is correct. U-tubes will always have some air bubbles travelling through them. As long as the flow is sufficient, the air bubbles will not collect at the top. I had a problem with air collecting when I first got my overflow. I increased my flow and have run problem free for 6mths. You should either increase your pump size or remove one of the u-tubes. As long as the overflow drain line can handle the amount of flow your return pump produces, the sump level will remain constant after the pump is running for a minute or two (closed loop system).

 

[mburnickas]

you are correct but you are going to start issues with the system. For example, If I have 2 u-tubes and has air in them, based on what you are saying I should get a larger pump. Wrong, that will lower the water level in pump since the u-tube has a certain max flow rate. It does not care if you have a huge pump or small pump, it only moves at a certain flow rate (volume per time). Plus the overflow is not driving the flow rate, the u-tube is.
I would get a larger u-tube and maybe a larger pump. It is not as "cut and dry" as you think...nothing is.

 

[jeepboy]

I agree an overflow's max flow rating will be a limiting factor, but if air bubbles are collecting in it with only one u-tube, then I would just increase pump size to get closer to the max flow of the overflow after accounting for head losses.

 

[mburnickas]

Again true, but I know from my sump if I do just that (increase pump GPH by opening ball valve) my water level drops. Then I have to increase water flow to sump (getting another u-tube, etc..)
It is a balancing game that no one will win.

 

[jeepboy]

When you increase your pump flow does the water level inside the overflow box in the tank increase? I think that is an indicator that the u-tube is not able to flow enough. I have a 1400gal/hr overflow and do not have a large enough pump to exceed its flow rating....my problem occured when I had a SCWD on MAG12, the SCWD reduced flow enough that air bubbles accumulated in the u-tubes....after removal of the SCWD, I have had no issues.

 

[mburnickas]

I am not Jeep guy but the largest dia I can find was 1 1/8 or 1 1/4'

 

[crm13]

Just a quick response to the initial post, but if you are getting air trapped in the U tube, and you are fine with the flow rate of your current pump, just try a smaller u tube until it stops. Just don't go too small or your overflow will not drain fast enough. But, by decreasing the diameter of the tube, you can create a faster flow-through which will take the bubbles with it. I had to do the same thing because the u tube that came with my overflow was 1.5 inches in diameter. I estimated the size of the tube I ended up using by using different diameter flex tubing until I had no accumulation of bubbles. The overall drain rate of your overflow will be dictated by your pump so your flow rate of the loop won't change... just the pressure through the pipe. HTH.