Plumbing question: When to reduce?

[salmon alley]

Currently my returns are plumbed with 3/4" pipe right up to the edge of the tank, where it reduces to 1/2" pipe and splits into two loc-line outputs.

There's a bit too much flow for the outputs to handle quietly, so I'm going to experiment with different pump sizes. Naturally the outputs vary.

Here are the pumps I'm considering:

 

Eheim 1260- 3/4" output

Eheim 1250- 3/8" output

Oceanrunner 2500- 5/8" output

 

Rather than having to replumb every pump I've come up with a possible solution:

I'm going to cut the 3/4" pipe and reduce it to 1/2" and put a Female threaded fitting on. Then I'll use threaded polyethlyene fittings with barbs to connect flexible tubing to the various pump output sizes.

 

So, my question is: should I replumb the whole setup with 1/2" pipe, or is it okay to go from 1/2" to 3/4" back to 1/2" again?

 

Sorry, I know this is a little confusing.

Edited January 1, 2008 by salmon alley

[Highland Reefer]

I added a shut-off vale to my setup so I could control the flow in the tank, then I added a return with a shut-off back to my sump right after the pump to relieve the pressure. Works Great. It's nice having the extra pump capacity for future add-ons. Plus I think the bigger pumps hold up better.

 

Edited January 1, 2008 by Highland Reefer

[johnnybv]

1/2" pipe creates a tremendous amount of friction loss in the pipes, thus requiring a larger pump. I reccomend using the largest size pipe you can, as far as you can, then use a valve to regulate flow.

john

[salmon alley]

1/2" pipe creates a tremendous amount of friction loss in the pipes, thus requiring a larger pump. I reccomend using the largest size pipe you can, as far as you can, then use a valve to regulate flow.

john

 

 

That was my initial thought, but if I'm reducing the flow of the 1260 down to the flow of a 1250, I'm using 65w to get 300 gph instead of using 28w to get 300gph, right? That seems awfully inefficient, AND I would think that the larger pump would have more noise/vibration associated with it.

Is my thinking flawed here?

[EBR]

Check out what dchild has to say here about plumbing sizes on 29 July 2007 (post #17). Made a world of difference on mine.

Matt

[johnnybv]

I am saying that with larger pipe you can use a smaller pump and get the same flow as using 1/2" pipe with a larger pump. As far as pumps go, with a valve on a larger pump you can get more flow, with a smaller pump, it is what it is.

john