overflow/return rate


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how do I know how much my reef ready tank can overflow? I want to beef up my return pumps but dont wanna over do it. ATM I am running 2 x 700 gph pumps. All the plumbing was done w/ 1.5" pvc. Was thinking of going to 2 x 1400 gph pumps but worry I will drain sump. Thanks for any help
Do you mean if the power goes off, how much space do you need in the sump to contain the overflow?
No, I mean if I can pump 100 gallons up and only 50 can come down I'm in trouble, I don't wanna over return.
Are you beefing up your return so you get more flow in your tank or so you get more of a turn over in your sump?
+1 on the ball valve

I run an external pump so I have one ball valve after my sump (so I can shut that side down if I have to pull the pump) and one after the pump (which could be used for throttling if necessary and also if I needed to change the pump).

If you only use one ball valve install it after the pump so you don't have cavitation issues.
By the way, I love the long horn cowfish. I had one for many years in my 150 and those fish have so much personality:mrgreen:
ahhh, ball valve, I'm trying to get more turn over in main tank.

Instead of increasing the flow from the return pump, you should just put in another powerhead in the tank itself or upgrade the ones you have to a higher flow rate.

But you should have a ball valve on the return line anyways.
Ball valves are there, I'm a dummy for not thinkin of that. I have a 125 display w/ a 75G sump/fuge set-up. Skimmer is below, shouldn't I have a decent turn over rate? I also run 2 aquaclear 75 power heads in display. I think I'll swap out one of the 700 gph return pumps for a 1400 ghp and leave the other pump at 700 gph, sound good?
I would put them both up to 1400 and maybe add a few more. I have two 1400 plus my return in my 46 bow.
Another reason I want this higher over turn rate is I still need to keep 2 heaters in the display tank, was thinking if faster turn over rate could put all heaters in sump so out of site, this work?
You should be able to move the heaters into your sump. That will get them out of sight.
Am I missing something or just not understanding? You want 2 1400gph pumps in your sump? so moving roughly 2400gph? I was wanting a mag9.5 for my return pump is my thinking wrong or are you just wanting to move some water!
If flow is your goal, you are better off just getting an extra powerhead or two for your tank than messing with the overflow and return pumps.
In my tank, a 45 I have a one return pump rated at 712gph. With headloss I figure it is just under 600. The rest of the flow in the tank is power heads. I dont think changing around the return pump for more flow in the tank is a good idea. It seems to me you are just asking for a flood. If what you have works then just add power heads to the DT. :twocents:
Am I missing something or just not understanding? You want 2 1400gph pumps in your sump? so moving roughly 2400gph? I was wanting a mag9.5 for my return pump is my thinking wrong or are you just wanting to move some water!

yes, 2 1400gph in sump pumping water back to main tank. My thinking is the more turn over the better seeing skimmer in down there and want all heaters down also so out of sight. I will replace 1 mag7 with a 1400gph pump and go from there, maybe replacing the other after.
According to some of the guys at MFK the expected vertical flow of a 1.5" pipe that is at least 20" and has no turns or bends is around 1350gph. But I have also read at flexPVC.com that it can flow up to 2100gph.

A fast way to calculate your current overflow rate is to hold a 1 gallon container under your overflow exit and time how long it takes to fill up. Take that time and divide it into 3600 (60 seconds in a minute, 60 minutes in an hour = 3600). That will give you the GPH on your overflow as it is running at that moment. If everything is working as it should it will match your pump output (minus head loss). (Water in, water out, always staying at the same level in the DT.)

So, if it takes 5 seconds to fill a 1 gallon container it would be 3600/5 = 720gph. If it takes 8 seconds you are flowing 450gph.

To tell if you can move more volume through the overflow, AND IF YOU HAVE ROOM IN THE TANK, turn the ball valve on your overflow down and let the pump add more water to the DT than normal. Then open the ball valve all the way, wait about 2 seconds and time it again. Waiting the 2 seconds should give the overflow enough time to catch up from the ball valve being since there will be more volume at the top. This will tell you what your overflow can do beyond what your pumps are doing.

I would only say that even if your overflow can handle it, adding a lot more flow through the it may give you an increased noise issue. It all just depends on what your acceptable levels are.