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Old 11-19-2008, 05:27 AM   #1
Pabs
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overflow rate


Anyone know how i can calculate my overflow rate into my sump. I'm using 2 x 11/4" pipe.
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Old 11-19-2008, 07:16 AM   #2
crvz
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Is that 1.25" pipe? Not sure what 11/4" means. And what are you trying to calculate, theoretical maximum overflow or actual measured flow rate into the sump?
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Old 11-19-2008, 09:44 AM   #3
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I need to know the max LPH that the two 1.25" overflow pipes combined can cope with so i can decide on which return pump to get for my sump (3000LPH or 5000LPH). I don't want to get the 5000LPH pump to find that the overflow pipes in the tank are to small to cope with that much LPH.
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Old 11-19-2008, 10:18 AM   #4
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Ok, 12 gpm of water can flow at 5 ft/sec through 1 1/4" sch 40 pipe. Thus you would get 720 gallons per hour per tube, so 1440 gallons an hour. This would give you a max of 5450 liters an hour. I think that with the factoring of tank height and head, you will be fine with the larger one. Usually a 5000lph pump might only give you 3000lph at 5 ft. So I would get the larger pump and put a gate valve on the return to scale it back a little if you find it necessary. hope that helps.

Here is a link to a chart to help. It isn't in metric, sorry...

I had to remove the www . and space out the link since I am too much of a noob on here to post links.

engineeringtoolbox. com / pvc-schedule-40-pipe-friction-loss-diagram-d_1147 . html
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Old 11-19-2008, 04:35 PM   #5
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Well, regardless of max flow rate, you should target somewhere in the ~5x system volume per hour flow rate through a sump. Though to answer your question, each 1.25" hole should be able to handle about 900 gph.
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Old 11-19-2008, 10:20 PM   #6
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too
much is better than not enough eh? you can always throttle the larger pump back with a ball valve
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Old 11-20-2008, 07:08 PM   #7
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Too much can be too much sometimes though. The 5X turnover is closer to a better number than what the drains can handle. Assume a 125 gallon tank. You would want roughly 750 gph through the sump. That the drains can handle it each on its own, gives you built in protection against flooding. Now, assume you can get a pump that will pump 800 gph and you restrict it by 10%. That's good to have. But, to take a pump and throttle it down to 25% or so of its max flowrate is simply way overkill. That overkill is what I had on my 90 with a mag18 return pump throttled down to around 500gph. Its a major pain to try to adjust the flow through the sump when trying to throttle it that much.
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Old 11-20-2008, 09:45 PM   #8
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dont want to highjack. but do you think my little giant at 510gph is to much pump for my aga rr 75 gallon? i have know idea my tank isnt up and running yet still pulling all my parts together
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Old 11-20-2008, 09:50 PM   #9
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Not it isn't Mike. Is that 510 after head loss or before? 5X is a starting number but it also depends on your skimmer. If your skimmer pump is only rated at, say, 300 gph, and you are pumping water by it at 510 gph, then you are essentially wasting the flow, wasting the electricity and simply pumping detritus in a big circle. But, if your skimmer has a 600 gph pump on it, then you are right about where you need to be. There isn't a basic rule as there are several things that play into the return pump.
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Old 11-20-2008, 10:04 PM   #10
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yes thats before head loss. but i'm less the 2'5'' to the bottom of the tank from the pump so i shouldnt have much head loss. my skimmer is a euro reef and with a sedra 3500.
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Old 11-20-2008, 10:37 PM   #11
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2'5" vertically, any other fittings? What does this calculator give you when factoring in your plumbing orientation:
http://www.reefcentral.com/calc/hlc2.php

It isn't exact but its close. The pump on your skimmer wont have head loss from the head pressure but will pump less than what a sedra 2500 pumps in a sump because of the air causing loss of water movement.

You can check the flowrate by timing how long it takes your skimmer to fill up a five gallon bucket from the drain, unless its a recirculating skimmer.
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Old 11-21-2008, 08:12 AM   #12
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it gives me about 470 gph thats a really cool calculator. Thats just a quick guess on other plumbing fittings on my part but it should be close. So I guess i'll be sucking it past my skimmer a little to quick eh?
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Old 11-21-2008, 09:20 AM   #13
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The closest analogy I have ever come up with, and it could be way off couse, but is to think about being in your car. Sitting still, you can breathe normally. Now, accelerate to 55 mph and stick your head out the window, facing sideways to the wind. Now, you can still breathe but its a different process to breathe. The only thing you would breathe in would be what happens to go right in front of your face. Where when you are sitting still you breathe in whatever your lungs can pull in. The same with the skimmer. If the flowrate is too fast, then things just get sucked right on by. If you can slow the flow rate down, then it allows the skimmer to pull in what it can manage to pull in, not just what happens to go flying by the intake and manages to get unlucky and sucked in. Not the best analogy but the best I can do at 10 in the morning (not a morning person, my brain wakes up about 6pm).
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