how much flow will i lose

[bigbill]

i am runing a mag 12 an i spilt it in to 2 3/4inch returns how much flow will i lose here is a pic of my return

[shovelhead91701]

http://www.dannermfg.com/infoS.asp#

should be what you need here

[jimsflies]

You'll probably be around 1000 gph...figuring you are around 4 feet of static head and will lose some with friction loss from the elbows, nozzels, etc.

[jolson10450]

bill, the only thing i see wrong is you put 90's on it. if there were a Y or 2x 45's on each side the flow would go up much easier. i cant say exactly the flow you will lose though.

in a perfect world if you split 1 pipe into 2 pipes you would lose zero flow, you would only lose velocity (the rate of speed at which the water comes out of the tube) but say you started at 500gph you would still have 500gph if you split it into 2 but it would just be at less speed because its over 2" of pipe instead of one.

good example is your garden hose always comes out around 30psi which is the usual city water. if you put your thumb over it you can shoot a further stream, it is still 30psi but you are increasing velocity by adding a smaller hole at which the water can come out.

[bigbill]

iam going to put heads on the pipes so the velocity should be ok

[rmalone]

The heads, which will increase velocity, will also decrease flow. So what? In tank flow is very important, return flow volume is WAY overrated. Now thats just my opinion but ... 1000g or even 900g would be plenty fine for your tank.
I run a ATB flow star 1500, in a 180g with about 4ft of head. I also run my little media reactor off the same pump via a pvc tee and a valve, and I stuff the return side (of the tee) through my 1/4hp JBJ chiller. SPS and RBTA's are loving life. At least for now anyway, lol.

[XSiVE]

ive run mag12 return thru two 3/4in returns with 90's and had lots of water velocity coming out, you've got nothing to worry about. probably around 1000 gph with head loss.