Increasing flow of a hang-on overflow box?

j_chicago

j_chicago

Usually Drunk
May 12, 2007
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Chicago, Il
Real Name
Jason
Well I got my plumbing done and fired up the pump, but I can't seem to get enough flow through the overflow U-tubes. Currently I have my Mag 9 throttled way back, like 2/3 closed on a ball valve. And the flow through the return is dismal.

I have two 1" U-tubes now. The inside box is set low in the tank now so almost the full height of the weirs are being used. And the water height is the same both inside the tank and inside box. The water height in the tank is about .5" from the top of the rim. The stand pipe is all 1" PVC, no flex, and only has two 90 deg angles. And I currently have that throttled back as well to tune the noise out, both gargling and splashing in the drain compartment of the overflow box.

Is my only option to add a third u-tube, or is there some other adjustment I can make?
 
There's no air bubbles, both tubes are full of water.
 
Sounds as tho you need more force to ush the water through, what about reducing the size of the pipe from one inch to 3/4 or half?
 
The reduction of tube size seems counter productive, but I'm a noob at this so I have no idea if your right or wrong.


The box came second hand when I bought it off someone so I have no idea what the rating is. The previous guy had it going through flex hose to a wet/dry. And he had a massive hobby pump as a return. So I'm sure he was able to get the flow higher.


I'm guessing I'm only getting about 150-200 gph if not less, when the pump should be about 750 gph after head loss.
 
Try pulling out the standpipe first, so you just have an open bulkhead in the bottom of the back part of the box. This should drop the level of water in the box and get the siphon tubes pulling more water. A 1" U-tube should flow a lot more than just 200gph.
 
The back of the box is seperated into 2 sections, one that the U-tubes go into, then that splashs over into the drain section.

I could cut the wall between the two to increase the distance, but I would want to do that as a last resort since it would an unreversible mod.
 
BTW, thanks for all the replies so far. Doing an internet search last night and all the results seemed very user specific and non-helpful for my situation.
 
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