docart30

sump for nanoreef

i have a 60 liter nanotank, and planing to build 20-25 liter sump for it. The minimal available overflow box is 2600 l/h. The pump which i have in mind is 2800 l/h (maximal flow rate). What do you think if the flow from that pump will be too powerful for 60 liters with corals?

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Use a valve on the output of the pump to adjust the flow into the tank for the overflow. This is safe as long as it is on the output, not the suction of the pump.

 

Do you know the diameter of the drain line on the overflow you're looking at? The ratings on those is all but meaningless because flow rates through a pipe are different depending on whether the drain is run vented or run at a full siphon. For example a single 1" PVC pipe is rated at something like 600 gph, which is the vented flow rate. At full siphon, it can run closer to 2000 gph.

 

In the case of a single drain line, you will need to run it vented and most likely will need to operate it at about 30% of rated flow to keep it silent. This also makes a valve on the return line absolutely necessary to dial in the correct flow rate for the overflow.

 

If you're interested, I can discuss the physics of how to keep one silent, but just a quick rule is that for vented overflows, around 30% is the nominal flow rate to keep it silent. So for a 1" overflow, this is roughly 200 gph. Any more and you'll either get gurgling or a toilet sound out of it. You can always do less though.

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Thank you for your comment. So it's desirable to make return pump work with approximately 200 gph rate to keep system silent? Will i need a valve on the return line for single drain syphon in that case?

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Thank you for your comment. So it's desirable to make return pump work with approximately 200 gph rate to keep system silent? Will i need a valve on the return line for single drain syphon in that case?

 

No. If you do a dual drain like a herbie, I would put a valve on the full siphon line, because you would likely want to further throttle the flow, again due to the very high potential flow rate of a siphoning overflow, but for a single drain, you want as little chance of clogging as possible.

 

And just very rough estimate, 200 gph is about the max it can handle and stay very quiet. But, you'll have a lot of head loss due to the height of pumping from a sump to a tank as well as from the friction of the tubing itself. So, to get an actual 200gph in the tank, you would need more like a 300 - 500 gph pump, depends on the specific pump though.

 

Best bet is to look up pump curve chart for the pump you're looking at and have a rough idea of how high the vertical distance is from your sump to the return, mine are typically around 5ft, for a tall 24" tank on a 36" tall stand.

 

So looking at a crude pump curve for the eheim compact pumps:

 

eheimcompactchart.png

 

Let's say I want my flow rate to be 330 gph, which translates roughly to 25 lpm. At 5ft, I would be needing to use the 3000 series pump, which has a rated of almost 800 gph. So in 5ft of vertical distance, I lose more than half the rated flow. Most charts are in gph so you don't have to convert.

 

Something like a MJ1200 is down to about 50 gph from about 300 rated, at 5 - 6 vertical feet. So when you look for a pump, do not go off the rated flow, but find a pump flow chart also called a pump curve and figure out the approximate flow rate at the height you will be pumping. Because of other factors, this is not always super accurate which is another reason I always go a little bigger and use a valve to control actual flow.

 

And you can always stay with lower flow, you don't need 20x turnover through your sump, I shoot for 5 - 10x turnover per hour, roughly 500 gph on my 90 gallon tank. There's no reason for crazy turnover on a nano tank either especially if it means you're constantly fighting to keep it quiet.

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