Determining return pump size

[keithrett]

I have almost finished building my acrylic frag tank, the only thing I have left to do is cut and place the baffles in the sump tank. In order to save time I would like to order the return pump and have it shipped while Im finishing the sump. My question is how do I know what size(GPH) pump I need? I have two 1" drains and one 3/4" return. The pump would have to pump the water up 3-5ft to the frag tank. (dont know if that helps) Do all pumps have a switch that allows you to tune the flow rate? Are there any brands I should stay away from? Any brands people would suggest? My friend mentioned something about a test that I might need need to do to see how many gallons my drains could handle in an hour, if this is true how do I do this test? If I missed any details, just ask and I will post the answer. Or if there is already a thread about this just post the link and I won't waste anyones time.
Any help is appreciated, I am amazed that I have successfully made it this far, I would hate to mess up now and order the wrong pump.
Thanks

 

[BLAKEJOHN]

Easy buy whatever pump you thing you might need. remember that with 3-5 ft of vertical pipe there will be a loss in the rate of flow. Dont worry about getting one that is too big cuse there is an easy remedy.

Here it is, off of the return pump you wil have a tee with two ball valves. One side of the tee will go to the tank and the other will go right back to the pump. Use the ball valves to control the rate of flow. Having the return back to the sump will prolong the life of the pump by it not being restricted. Mag pumps are primarily used for returns.

 

[nos2074]

how big is your tank. I like mine to turn over between 5-8 times or so an hour.

My example:

I have a 125gal DT and about 30gals in my sump, total being like 155gal.

I have a Mag-18 for my return and about 5' of tubing from my sump back to the the DT. AT 5' a Mag-18 pumps 1100 GPH. 1100/155= about 7. So my tank turns over like 7 times an hour.

How much water volume do you have and I will help with a Mag drive pump

 

[r2d2]

You have to know your overflows max capacity or max flow rate.
Then you have to choose a pump that @5ft delivers that flow rate or a little less, and always looking for that turns per hour that Dion talk about.
If you choose a very large pump you will overflow your tank because water would not drain at same rate that pump is delivering.
If you choose a very small pump, water levels will be fine but you will have a very low filtration rate through sump.

Greetings

 

[keithrett]

The tank is 50 gallons with a 40 gallon sump. As for the total water volume, I am unsure because I have not set the baffles in the sump that will deterine the water level.

 

[BigAl07]

You don't have to worry about being that specific for this part of the equation.

You do need to know how much flow your over-flow will bring back to the sump. That is mission critical.

 

[BLAKEJOHN]

Depending on your overflow a mag 7 should do just fine. A mag 9.5 will also work but you may have to dial it back. Two 1" drains (drilled into the tank)can handle either of these pumps just fine.