Overflow boxes

[pnikiel]

Hello all,

Looking for some advice.

I need to buy a new over-flow box and I'm trying to figure out which size to order. I have a 125 gallon tank. Manufacturers recommend a 600 gph model. If I wanted to upgrade to improve filtration, would I need to replace my return pump? Should the gph rating of the over-flow box match the gph rating of the return pump?

Thanks.

 

[Sascha D]

There are many ways to upgrade your filtration. What are you currently running and what were you trying to upgrade?

Your overflow should be higher rated than your return pump.

 

[pnikiel]

my skimmer is rated for a 200 gal tank. But I thought since I was replacing the the overflow box that ran water through my refugium I could consider over-treating the water in my tank.

So if I were to move up to a 800 gph overflow box I should upgrade my return pump? To what? It has been working for me for 4 years now. Should I be concerned?

 

[pnikiel]

right to the point... if i go with a 800 gph overflow box, how big a pump should I be thinking about?

 

[ac7av]

If you want to get the full benefit of the 800 gallons then you need a pump that will return 800 gallons to your tank. Take into account the reduction of the water flow from the pump because of the vertical distance and angles on the return line and so on. You need to be careful there you don’t want the flow of the return pumps to exceed the overflow. If you do this with out safety measures in place you could overflow your tank. For example I have a 1400 gph overflow, I have two 1090 gph pumps returning the water. Because of the restrictions and vertical height the water is pumped I am only getting about 1200 gph returned to the tank. The bottom line is bigger is better (at least I think so) in the over flow box if you have the room. You can do all the regulation with the return of the water.

 

[aquariumdebacle]

Overflow boxes = overflow onto the floor! Avoid them if you can; if you cannot, oversize them as much as you can afford.

 

[Sascha D]

I've never had a problem with an overflow box. You just have to make sure that you get one big enough to accomodate your return pump. When buying a pump, look at the 3' return rating to see a more accurate estimate of how it will perform. Keep in mind that the pump will have wear and tear and over time pump less and less.

The only thing that really affects the gph rating of an overflow box are the size of the drain holes and the length of the box. The length doesn't even really matter that much, except to reduce noise. If you narrow a creek, it isn't going to have less flow, its just going to move faster

 

[pnikiel]

Has anyone had any experience with the Continuous Siphon Overflow boxes? They sure cost a lot more. But could be worth it if they are indeed quieter and can restart on their own after a power outage.

 

[ac7av]

I thought that is what you were talking about from the start. Like I said I have one it is a 1400 gph and I have never had a problem with it starting. I shut off my pumps every day to feed and turn them back on after an hour. I have never had any problem with them starting. That is never a problem. The problem you will experience is air getting into it during the operation in some boxes. This situation will not cause the overflow to stop working but it could slow to equal the in coming water. I have to be careful of the surface agitation of the tank water, if it is too turbulent at the box inlet you will have problems with air. I have done a modification to mine to eliminate that problem but it is something to watch for. There are also information out there to quiet overflows and the filters in the CPR boxes I don’t think work very well, you still have the overflow splashing water. I have made a filter that eliminates 75% of that noise and you don’t have to full around with the pvc tube and vent mode you will see out there. It will work but needs tinkering with to get it just so and will get out of adjustment every so often. TMW for me.

 

[atavus]

What were the modifications you made to remove the bubbles accumulating in the tube? Filter media in the box?

 

[ac7av]

The box I have is a knock off of the CPR brand. 1400 gph with one 2 ½ in drain. On the top of the box there is the tube connection to connect a piece of ¼ in tubing to the very top of the box so you can vacuum out the air. What I did is put a piece of tubing that was 2 feet long on it and run it back down into the outlet side of the box and coiled the excess around the bulkhead fitting. This area, because of the bulkhead fitting always has about a half of and inch of water in it. When the pumps are on and the overflow is working, because of the water pressure water will also travel threw the ¼ tube and immediately removes any air that goes into the box. I don’t know the physics of the whole thing but is seems to work in this case. I have on a few occasions had to re prime the line a time or two but is has always been when I am messing around in the tank causing waves. Because both ends are always in water when you stop the pumps no air gets into the line. I will admit its not perfect but is eliminates 95% of the constant hassle of getting air in the box. Someone may have come up with something better but as far a simplicity goes, a 2-3ft piece of tubing is as good as it gets.