overflow box

[mussel20]

My u-tube in my overflow box that goes from the box inside the tank to the box outside keeps getting air in it. My box is skimming of the top of the water and can't be moved down anymore. Does anyone else have this problem that could help me? Any suggestions would be greatly appreciated.

Also, I have an oily fim that won't go away on the top of my water. Everyone said when I got a sump it would go away but it hasn't. Any thoughts?

Thanks Jeff

[Andrew]

Try leaning one end of the overflow box down into the more than the other end. This will make all the water flow into the box at the end end and than put the u-tube at the other end and that should stop bubbles/air from entering the u-tube. If you also increase the flow going through the overflow box, the bubbles will go into the u-tube and out the other end. The flow will be greater and the bubbles will be carried with the water flow and not have time to stop and collect.

[sjm817]

What is odd here is the two problems you are having are usually caused by opposite issue. Bubbles in the U Tube can be an indication of not enough flow. Lack of surface skimming can be an indication of too much flow.

What exact overflow is it? How is it plumbed? What is the return pump?

Can you post pictures?

[mussel20]

I can't post any pictures, sorry.

It is an eshopps brand overflow, the smallest one they make. It is plumbed with rubber tubes going to and coming from the sump. The return pump is a Mag 7 that feeds into and scwd. There should be enough flow through the boxes because I can suck all the air out of the u-tube and it be completely full of water with no bubbles, and then about two days later it will be really full of bubbles and the tank will start filling up because the return is moving more water than the overflow.

Thanks,
Jeff

[sjm817]

I think I know the one. Does it have a shallow skimmer box and a high rear baffle? Where is the water level inside the skimmer box? Same level as the tank? Below the teeth?

[mussel20]

Yes, the water level in the overflow box is the same as in the tank, just below the top of the teeth, maybe a quarter of an inch.

[sjm817]

That is why you are not surface skimming. The water has to "fall" into the box to surface skim. If it is at the same level, it wont work. Is the drain from the overflow unrestricted?

[mussel20]

The drain from the overflow is unrestricted besides their is a sponge filter down the drainpipe. I don't think I can get the water in the box to be lower than the tank water because it equalizes itself out if i'm not mistaken.

[sjm817]

I hate to say it, but that overflow is the problem. I tried to help someone else with one of them and we could never get it to work right. The skimmer box is too shallow and the rear baffle too high. Its a poorly designed overflow. Can you return it?

[sjm817]

Maybe try raising the skimmer box up. This might get the flow moving through it. The idea is the level in the inner box is higher than the level in the outer box.

[mussel20]

No, i bought it used at a fish store for cheap, I assume that someone else returned it because they had problems with it. My brother in law has an overflow that is CPR and he never has any problems with his. Is that the way to go, or is there a better one than that?

[sjm817]

UGH. The CPR is a really bad overflow for other reasons. You want a U Tube overflow, but not the one you have. This is for a 75G?

I'm going to recommend THE BEST overflow in the business. This one will work very well. You wont have problems with it. Lifereef (http://www.lifereef.com/siphon.html). Yes, it costs a little more, but it is worth it. If you do want a cheaper overflow, post back.

[mussel20]

anything a little cheaper? Why are CPRs bad?

[yeame]

marineland makes a S.O.S. overflow that is the best I have used and is like $75

[sjm817]

CPR's cant keep a siphon on their own. They rely on a vacuum pump such as an Aqualifter to remove accumulated air. They are unreliable. A decent U Tube overflow needs nothing to maintain a siphon other than the laws of physics.

Amiracle also makes a very good reliable overflow. Amiracle $60 (http://aquacorals.com/ShopOverflows.htm)

BTW, I've owned Lifereef, CPR and Amiracle overflows.

[mussel20]

Thanks sjm817. I will think about all of these. Thanks for the help, hopefully when I get one it will work better.

Jeff

[75reef]

A smaller u-tube will increase water flow and rush bubbles into the outside box. A 3/4" u-tube will flow about 400-500 gph. You should take the foam off of the standpipe, it is a nitrate factory and a plankton killer.

[sjm817]

The 3/4" U Tube wont help in his case. It would actually make it worse. The slow flow through the tube is due ti not enough of pressure difference between the skimmer and drain box.

I have another idea for this thing. The main problem is the high baffle in the rear box. Could you dremel it down? You would want it so that it is about 1/2" higher than the bottom of the U Tube. Another way would be to put the U Tube in the same side as the drain, and put in a short piece of PVC as a standpipe to make the height again, just a little higher than the bottom of the overflow.