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-   -   how much gph will flow through 1.25" drain pipe? (

Jereli 04-01-2011 06:40 PM

how much gph will flow through 1.25" drain pipe?
so my question is how much flow can i get from a drain pipe that 1.25" going into my sump? the drain pipe starts from the top on my tank with over flow box so there isnt any pressure on it. how much is flowing down into my sump? i have a rio 2500 return pump but i have to cut it down alot on the return line so it wouldnt be faster then my drain. i want to get a different pump that i can run fully open to match my drain. any help appreciated.

Gti_Leo 04-01-2011 06:55 PM

it all depends on the pump pushing it and the head height. genereally the higher you go the less the flow but also the wider you go the heavier the water so the pump struggles more then it would with a thinner pipe

Jereli 04-01-2011 07:00 PM

thanks i have a fair understanding of the return side but my question is on the drain side which i dont understand how to figure out the flow rate of the return. i currently have my water draining into my sump through a 1.25" pvc and was wondering how much flow is actually going through there?

ccCapt 04-01-2011 07:05 PM

A 1.25" PVC is capable of doing aprox 900 gph, but how much is actually flowing thru it depends on your return pump. If set up properly, the drain will only flow as much as the return pump pushes back into the sump.

Gti_Leo 04-01-2011 07:06 PM

if its gravity then as much as the pump is pumping. the water will flow i nthe overflow box and down to the sump.

Jereli 04-01-2011 07:16 PM

i dont really understand sorry lol... so my drain pipe is a 1.25" going into my return pump is a rio 2500 which is rated at 782gph which is most likely less due how much the return line rises. but if i fully open my return pump it seems to be pumping out faster then it drains. does this sound right? thanks for the quick replies by the way

redneckgearhead 04-01-2011 07:24 PM

Try this http:// site It gives the flow rates of PVC.

ccCapt 04-01-2011 07:36 PM


Originally Posted by Jereli (Post 1279172) on my tank with over flow box so there isnt any pressure on it. .....

What kind of overflow box is it? If it's a u-tube style, what is the diameter of the u-tube?

Jereli 04-01-2011 07:39 PM

ahhhh ok i understand now. i just fully opened my return pump and you guys are right its now draining at the same rate as me returm pump. and i was about to buy more power heads for more flow but i just got alot more flow now that me return is rully open. thanks for your guys help i really appreciate it. for some reason when i seen my return pump section of my sump going lower i thought it was going to keep doing that until it ran dry but it actually ends up leveling out. thanks

Jereli 04-01-2011 07:40 PM

i drilled it. the overflow box is inside the tank.

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