Plumbing the return with PVC

[SnowHeart]

Short Version: If the return line from the pump is 1 1/2", what size should the pipes be after splitting at a "T" to feed the tank?

 

Long Version: After taking a closer look at what will be my return pump (a Mag 12), I remembered that it says you need a 1 1/2" diameter pipe for maximum flow. (This meant I had to scrap the idea of a SCWD with a 3/4" diameter.) So, the beginning of the return line is 1 1/2" and that goes up about 4 feet from the sump to the tank, then there will then be a "T" to split the return to a couple of outlets. Obviously, that pipe after the "T" doesn't need to be 1 1/2", but what size should it be? (I seem to recall that a 3/4" diameter actually has less than half the volume, so maybe it should be 1".)

 

Thanks all.

[flowerseller]

1 1/2" in/out on a mag 12?

 

Not

 

1/2" in/out?

[SnowHeart]

1 1/2" in/out on a mag 12? ...

Yup. I know. I scratched my head on it, too. The inlet and outlet on the Mag 12 are actually 3/4", but it says for maximum flow on the return the pipe should be twice the diameter of the outlet, so 1 1/2"... seems like a LOT of water to me, but... (Maybe I'm having a total brain fart?)

 

If you follow this link and then look underneath the first chart on page 2, it says 1 1/2" is the MINIMUM size pipe for maximum flow. Says something similar over on Melevsreef.com discussing the closed-loop prototype he built:

 

The Mag pump comes with printed instructions that state to double the outlet size to determine the plumbing needed. The Mag 7 has a 1/2" outlet, and the pvc needs to be 1".

Edited October 22, 2008 by SnowHeart

[Vader]

I would call the manufacture and ask to speak to someone in tech. support. That just sounds nuts imo

[paenian]

To answer your question, a little geometry:

The cross sectional area of a pipe is pi*(diameter/2)^2.

 

Approximately:

1.5" => 1.77"

1.25" => 1.23"

1" => .78"

.75" => .44"

 

So I'd recommend 1" pipe after the split with only a slight total throughput loss, especially given that the T will cause a loss by changing the flow direction. Of course, the smaller the pipe diameter the more laminar loss (friction with the sides of the pipe), but it would be negligible.

 

Paul

[SnowHeart]

Paul: Thanks! Really appreciate the help with the math there. (I think most lawyers go into their career not because they love the law but because they hate math.)

 

Vader: I sent an e-mail to Danner yesterday (only address I could find was sales, though). Hopefully I'll hear something back. I think it's odd, too, but when I ran it through the headloss calculator on Reef Central it showed 1000+ gph even after the 4' of vertical 1.5" piping and everything else. (I seem to recall that's a loss of 350-400 gph from peak, or about a third... so maybe it does make sense.) Oh well. One way or another, it either works or it won't. And, once I finally get this thing setup, I'll be sure to share the results and probably start by own dedicated tank thread with the trials and tribulations.

Edited October 23, 2008 by SnowHeart

[gmubeach]

Don't mean to play Negative, but have you cosidered what happens when a snail gets stuck in the outpipe.... just a heads up its happend to a few people on the forum.... For the tank I have listed its got 2 overflows at 1" each on could of handled the mag5's preformance anyway better safe then sorry!

 

I may of missread ingore my comment! I'm not an engerineer, but I can always count on biological life to upset mechanical designs.

[SnowHeart]

Do you mean the overflows or the intake on the return pump? For the return pump I was going to use the supplied foam prefilter. For the overflows, I doubt any snails will survive in the main tank (snowflake eel??) but the overflow boxes (from lifereef.com) are also slotted around the rim to allow water in, and then there's going to have to be mesh, wire or something else cover the top so the eel doesn't get into it. Am I missing something?

 

(deleted last part; brain fart)

Edited October 24, 2008 by SnowHeart