Help with overflow box

[andy281]

I have a 55 Gallon FOWLR tank that i have had set up for around 4 months. I did all the pluming to the sump myself with PVC. My problem is my overflow box can’t keep up with my return pump. If i open the valve on the return pump outlet hose all the way open the water level rises quickly to the top of the tank and will overflow if I were to let it. I only have two elbows in my drain line to the sump. I have been running the tank with the valve about 40% closed on the return pump matching the amount of water that drains to the sumo with the amount of water the pump returns. My overflow box is rated at 800 GPH and my return pump is rated at 700GPH. I’m confused because the head pressure should slow my return pump down even more yet i still have to dial it back. I have the overflow box adjusted all the way down to the lowest water level. Any suggestions I’m ready to add a second overflow box but I really don’t want to or see how I would need to. I just want to be able to run my return pump wide open to maximize the flow rate.

[Sniperhank]

It sounds like it is just fine. There are 2 elbows, most likely 90 degrees. There is an amount of headloss that isn't being considered here. As long as you have a ball valve to turn on the return side of your powerhead to restrict the flow you'll be fine. I don't know of anyone that runs their return pump without being restricted in such a manner.

[Dav3]

What type of overflow are you using?

[andy281]

Originally Posted by Dav3

What type of overflow are you using?

Eshopps PF-800


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[Dav3]

Is there some air trapped in the utube? If so, this can can slow the flow through.

Sounds like maybe the return pump is undersized and you aren't pushing enough water through to flush the air out.

[Dav3]

Have you used any headloss calculators to determine the aprox flow rate of the return at the display?

What is your return pump and what is the return plumbing? PVC or flex tube? Diameter? Vertical distance between pump and top of tank?

[lstimpy]

Try putting another U tube from the tank to the overflow box.


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[lstimpy]

Meaning two U tubes


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[Dav3]

If the pump is undersized, adding another utube won't help.

[andy281]

The pump is not undersized it's rated at 700 gph any my overflow Is rated at 800 gph my problem, is I want to open the valve on my return pump more but my overflow box isn't keeping up. If anything my pump is oversized I have to keep it dialed back to keep my tank from over flowing.


Aquatic-Airman

[Dav3]

Your pump is not oversized. That overflow is set for 800gph. You need to be hitting 750gph after headloss.

Check the utube. Is air trapped at the top?

[andy281]

Nope no air at all when I start the siphon I make sure I always get all the bubbles out with the airline tubing


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[Dav3]

What about after running the return for a few minutes? Does air build up in the tube.

[andy281]

No I have no problems with air In the tube. And it keeps the siphon during power outages.


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[lstimpy]

I had the same issue, fixed with a second u tube....


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[andy281]

Originally Posted by lstimpy

I had the same issue, fixed with a second u tube....


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Awesome! That's what I was thinking about doing


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[lstimpy]

I hope that works! My sump was going dry until I added a second tube. 😊


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