Lock Line Return Flow ?

[rocket]

I was wondering if I should use 3/4" or 1/2" lock line on my sump return. I plan to use a Mag 9.5 for the return, then use 3/4" black flexible tubing from the pump and "y" it into the tank with two return lines with lock line.
Should I step it down to 1/2" lock line for better flow? The chart for the pump say that at 4' the flow (with head loss) will be about 800gph.
The tank will have (1) seio 1100 and (1) maxijet 1200 for circulation.

 

[Krish]

I used the 3/4 lockline coming off of a mag9.5 I had on my old 38gal and liked the flow much better than when I tried putting the lockline reducer on the end to drop it to 1/2 inch. The 3/4 seemed to work out much better for me

 

[rocket]

Cool, I was hoping you would chime in.

 

[Krish]

LOL! No problem

 

[aquariumdebacle]

I plan on using the reducer with the 1/2" split into two directions.

 

[IAP Brian]

Should I step it down to 1/2" lock line for better flow?

stepping down to 1/2 will not give you better flow, it will produce pressure. The 3/4 will give you max flow but at 800 gph it won't feel like a blast of water. If you reduce and split it into 2 1/2 returns, you will keep the flow and also pick up some pressure.

 

[rocket]

So Brian, you think it would be best to run 3/4" supply line "y'ed" into (2) 1/2" lock lines? That way Ill keep some presure for current?

 

[Krish]

The only problem I had with the 1/2 inch was the nozzles are so small...Even the flare nozzles so I personally didn't get much surface aggitation (which was what it was intended for) out of the 1/2 when I use it for the return. When I used the 3/4 however (with the flared nozzle) I could ripple the whole surface of the tank (24x18). I guess you'll have to try it both ways. The parts don't really cost much at all and if you're like me, I like to keep changing up things until I find something I really like

 

[Meche]

stepping down to 1/2 will not give you better flow, it will produce pressure. The 3/4 will give you max flow but at 800 gph it won't feel like a blast of water.

That is not entirely accurate.

If you step down to 1/2 instead of 3/4 locline you will reduce pressure, increase velocity, and reduce flow rate.

I'm not sure what your defination of better flow is, but if you use 1/2 (instead of 3/4) you will reduce flow. However, it will be slower.

It sounds like Krish has personal experience with this exact same set up.

Hey Krish, do you have the pics of your 38gal half full with the pumps running? Do you have one of the Mag9.5 too?

If you reduce and split it into 2 1/2 returns, you will keep the flow and also pick up some pressure.

That is inaccurate. The cross-sectional area of (2) 1/2" locline is .393 sq in. The corss-sectional area of (1) 3/4" locline is .442 sq in.

With a smaller cross-section you will have less flow, higher velocities, and lower pressure.

 

[Krish]

Hey Krish, do you have the pics of your 38gal half full with the pumps running? Do you have one of the Mag9.5 too?

Hey Brett! I only have a shot with the closed loop running with the tank half full, but not with the mag9.5 running with the tank half full.

Attachment one is the 3/4 lockline "Y"ed into (2) 3/4 nozzles. You can see the difference in flow pattern between the round nozzle and the flared. This is the flow I got out of a 1506 gph pump at it is shared with a bottom output as well which means I had 2 bulkheads for each pump (2 Quiet One pumps total). The pumps output was 1 inch and I used (2) 3/4 bulkheads in the tank and this is at 1506gph per side.

Attachemt 2 shows the surface aggitation from the single 3/4 output coming from the mag9.5. The 3,000 gph of flow I had with the closed loop stirred it up some, but the mag drive did it's job as well.

Attachment 57 shows the difference between the 3/4 lockline and the 1/2 inch. The 1/2 round nozzels are the same size as the output for a maxijet which isn't big at all.