I Hate My Overflow (How To Fix It?)

minerva · #1 01-20-2010, 05:13 AM

My tank is not drilled - I have a HOB overflow. When it works, it works well, piping water down to the sump below my tank. The problem is, it regularly gets bubbles stuck in it. That breaks the vaccuum and then I have to clear out the bubbles and create suction again to get it working.

My current 'fix' is putting cotton batting in the entry to the overflow, as that seems to filter out the bubbles. Obviously, it gets clogged up and becomes a nitrite factory and has to be changed every few days - a little more hassle than I'd like.

Is there another soul in the world that uses a HOB overflow? How do you deal with the bubble issue?

mark · #2 01-20-2010, 05:20 AM

You'll see some HOB that will have a little fitting on the top of the "U" hooked up to the venturi port on a small power head or a Aqualifter pump to draw out the air.

#3 01-20-2010, 06:35 AM

I have a fitting hooked up to a aqua lifter no problems here.

Bill

sphelps · #4 01-20-2010, 01:15 PM

You're not moving enough water through the overflow tube, a higher flow rate will prevent bubbles from building up.

NuraNori · #5 01-20-2010, 08:11 PM

We have a HOB overflow with 2 removable U-tubes moving the water. Once one of them kept building up bubbles b/c we put it in backwards (one side is slightly longer than the other)...other times we just kinda move them from one side to the other until we find the "sweet" spot. There is only like an inch of play but it makes a difference whether the tubes are pushed to the left or right side...

Not sure if this is of any help

but I tried...

Chase31 · #6 01-20-2010, 09:37 PM

i have a CPR one and its doing sorta the same thing the pump takse the big ones out if there in the way but the little ones build up :s

minerva · #7 01-22-2010, 02:14 AM

Well. I don't have a pump / Aqua Lifter on it so that is probably 99% of the problem. Thanks so much for pointing out a simple cheap fix to this newbie. I'm going to get one right away and hopefully my siphon-breakage problems will be over!

-minerva

Chase31 · #8 01-22-2010, 02:28 AM

if you get one of the aqua clear powerheads you have a powerhead and a pump in one, only problem is this adds micro bubbles to your tank (why i stopped using it)

RuGlu6 · #9 01-22-2010, 03:21 AM

Quote:

Originally Posted by minerva

Well. I don't have a pump / Aqua Lifter on it so that is probably 99% of the problem. Thanks so much for pointing out a simple cheap fix to this newbie. I'm going to get one right away and hopefully my siphon-breakage problems will be over!

-minerva

Aqualifter is good fix however they get plugged themselves as well. So you will need to check on that pump periodically, which is a PITA and you will get tired of it eventually.

Now assuming that your over flow is Not CPR, then please see below..

The amount of the water flow that was mentioned earlier is one of the possible causes, when you have slow flow say 300 gph there isn't enough momentum to push bubbles forward in to the "U" pipe.

Next thing you can try is to lower your "Inner Box" down as if you would want to lower the level in the display tank. By doing so you will make sure that "U" pipe is completely resting on the lip, and submerged as much as possible on both sides (front & back).
Long side in to the outer box, short side in to the inner box.
This will get more "suction" (area with less pressure, or slight vacuum) in the section of the "U" pipe in the outer box so when bubble forms it will be sucked out.

Hope this helps.

sphelps · #10 01-22-2010, 03:13 PM

I would personally avoid a system using an aqua-lifter or similar pump. It opens up way more potential for failure. If you size things properly and use the correct flow rate then bubbles should not build up in the tube and you should never loose siphon.

Your system should be designed to make floods next to impossible. Your sump should be designed so that the return pump runs dry before the display can overflow in the event of a siphon failure. This usually requires an ATO however if an ATO is not an option then a simple float and relay system can be used to shut off the return pump if the water level in the display gets too high. To prevent siphon failure in the first place you need to size your overflow correctly to the return pump, going bigger isn't better for siphon overflows. You typically run return pumps at half there full scale rating with total head loss. This means if your return pump is rated at 1000GPH your overflow should be rated at 500GPH.