Backyard Aquaponics
A place to discuss aquaponics

I'm confused According to Timmons, the ratio of bottom drain to side drain at appx 1 to 4. If 2" drain at 20gpm, and 4" at 75gpm, this should be the correct sizes. I spoke with a man yesterday who I'm considering purchasing a RDF from and he says that 2" bottom drain isn't large enough??? I'm running a 100gpm pump and with 3 tanks to start and a fourth to come on line later. I should have appx 1500 gpm per tank.
Do I need a 2.5' or 3" bottom line drain?

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So many variables.

Side drain but where are you sucking from and where is the outflow...heights..

Bottom drain... but where is it being delivered to..

Ie.. you may be sucking from the bottom but delivering up to a raised receiver, defeating the pressure head advantage of the bottom drain... ( but you will be removing bottom solids)
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2" drain should be big enough, provided there is enough of a drop for the gravity to work. Make it too big and stuff will build up in the pipe.

You would be amazed at some of the lack of knowledge amongst sales reps.

1.26L/s gives you a velocity of ~0.64m/s. I would have said that was bang on the money for a solids conveying drain. If you went up a size the drop in velocity would be below flushing velocity.

The 4" drain is on the money as well.