GPH Math Overload on a new 90 gallon

Siberwulf

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Ok, so I'm trying to do the math on my new build, and it's... a lot. Here's a couple thoughts I had:

  • 90 Gallon Bottom Drilled.
    • 2x 1.75" holes (1" Bulkheads) - Source
    • 1x 1.5" hole (3/4" Bulkheads)
    • 22" linear drain space in the middle internal overflow
  • 29 Gallon Sump
  • I'll be running the overflow in a Herbie style
  • PVC (Schedule 40)
    • Gate Valve for the main drain so I can fine-tune
    • MAX 62" of Length
    • 56" of Lift
    • 1x 90 degree
    • 2x 45 degree
    • Head Pressure should be around 9.3' ???
  • VarioS 4 - 1056 MAX GPH - https://reefoctopus.com/product/rodc-pumps-varios/

Here's my questions: I'm assuming that 750 GPH is reasonable. 900 GPH is ideal, but 450 GPH is the bare floor.

My plan in my head is to use the 3/4" for a return. Should I actually use the first 1" as the main drain, second 1" as a return, and then use the 3/4" as the dry/wet emergency? This seems scary as the return flow could outpace the drain's ability to keep up.

If I go with the 3/4" as the return diameter, then am I going to run into issues hitting the 750GPH target?

I'm estimating that a VarioS 4 should be able to meet the 750 GPH target in either scenario...

Please, someone help my math. I've googled calculators for two days now. Thanks SO much in advance!

SidePipes.png
 

Rubberfrog

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Remember that not all of your flow has to come from the return/sump. You'll want some powerheads in there to direct the flow as well. 750 gph just from the return doesn't leave a lot to play with.
 

Gtinnel

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Does that mean I don't need to turn over the tank 10x an hour? Or did I read that whole thing wrong?
IMO you only need enough flow through the sump to keep water flowing to your filtration, and keep the tank heated assuming the heater is in the sump. I only have about 5x through my sump. The rest should come from powerheads in the display.
 

Potatohead

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I would buy a pump rated about ~800 gph. With normal head height this will fall around 5-600 which is great for a 90g tank.

In terms of which drain or return to use I would use 1" for the emergency and then whatever the pump you choose says to use for the return. If that is 1", that leaves you with the 3/4" for a drain which is more than enough if it is in full siphon.
 

homer1475

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I have an 80G cube with 30G sump. I use a waveline Dc2500(660GPH with about 3 foot of head, so roughly 450GPH) for a return and thats perfect on 100% for me.
 

homer1475

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Forgot to add....

Center tower style overflow with 2 1" holes(herbie setup), and 1 3/4" return(3 holes in glass) split with a T in the overflow out to 2 1/2" RFG nozzles.
 
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Siberwulf

Siberwulf

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So, this was enlightening! With all that said, should I be looking to step down to a VaioS 2 vs a 4? The 2 has a MAX GPH of 792 vs 1056. It'll be cheaper for sure.
 

KStatefan

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So, this was enlightening! With all that said, should I be looking to step down to a VaioS 2 vs a 4? The 2 has a MAX GPH of 792 vs 1056. It'll be cheaper for sure.

That would only be around 200 GPH with your 9.3 feet of head
 

Potatohead

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Well subtracting your sump water level you should have about 3.75 - 4' of head pressure. Maybe call it five with some bends? I think your 9 is too high personally. So the 2 should have about 400 gph which is fine, but if you go with the 4 you can always turn it down a bit.


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ca1ore

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Few thoughts:

1. Nominal 90 gallon tank probably only holds 80 gallons .... and that's before rock displacement.
2. 5X thought the sump is more than sufficient .... I tend to go closer to 3X.
3. Use the 3/4" as your return and the dual 1" as the drains. Plenty of pumps that will move 400-450 through a 3/4" pipe.
 

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