closed loop help

[Blackacid]

Having some problems with my closed loop in that I don't get any significant flow at all. Below is a diagram of my setup:

I am using a Mag 12 to power the loop.

Intake --> 1" PVC into 3/4" vinyl hose.
Return 1: 3/4" to 1" pvc return with 3/4" loc-line on end
Return 2: 3/4" to 1" pvc return with 3/4" loc-line on end


When I put my hand in front of the return flanges... I can barely feel the flow. If I shut down one of the return pipes the flow increases but it's still pretty low. The pump seems to be working fine. I'm just guessing it's not able to do what I want. Though I thought I'd rule out possible plumbing issues as well.

 

[Chrsnwk]

you didn't mention what kind of distances we are talking about here, but I'm going to assume the pump in in the stand below the tank. your intake line of 1" which goes down to 3/4" is smallish, and your return lines are biggish. Mags "push" water better than "pulling" it. The smallish 1" intake is restrictive, further restricted by the necking down to 3/4" tube. if you are able, upsize this as much as you can and do the reduction to 3/4" as close to the pump as you can. 1-1/4 or 1-1/2 all the way would be ideal, and avoid sharp 90 degree elbows. For the outlet, I think you are fine thru the "T" but I'd switch to 1/2" lockline to increase the velocity of the flow. Think in terms of a nozzle on a garden hose.

These 2 changes should net a noticeable result. The change to the intake will give you the most bang for your buck, you never want to starve a centrifugal pump.

 

[silverwolf72]

Plumbing sounds fine.

 

[Shagsbeard]

Your pump might be cavitating. You need to prime it somehow. You can do this by aiming a powerhead's output into the intake hose.

 

[iflipsidei]

ya the 3/4" might be hindering your CL

that mixed in with the T split is making each outport have half the amount of flow so each outport is probably getting about 500gph, just a guess thou from the head calc

 

[Blackacid]

I have an Ocean Runner 3500 on my sump's return with the basic connection 3/4" into 1" PVC, and exiting through 3/4" loc-line. That is very noticable flow and will actually agitate the water very well. When I shut down my closed loop to a single intake, and a single return the flow is still pretty weak.

Is the 3500 that much "better" than the mag12 in terms of pushing the water? I think I have the proper fittings to run 1" from the closed loop's return all the way to intake on the pump. I will give that a try tonight. Thanks for the suggestions thus far.

I'm considering switching to a Mag24, but perhaps a different pump type would be better suited for this application?

 

[Chrsnwk]

If you up the size of the pump you are still going to run into water starvation issues. You need to feed the pump and the non pressure side needs to be oversized to account for frictional losses in the supply plumbing. If you can't upsize the intake, a 2nd parallel intake T'd in at the pump can also be used to deliver the necessary volume of water.

This is a thread with some information on oversizing the supply line that was in answer to a problem I had some time ago...

http://www.reefcentral.com/forums/showthread.php?s=&threadid=884301&highlight=pump+noise


Good Luck!!

 

[jmait769]

I agree with Chrsnwk - 1 ½” inside diameter is the minimum hose size that should be used for maximum flow is what Danner recommends for their pumps. Here is a link to the <a href="http://www.dannermfg.com/InstructionSheets/PDF/9.5-12-18magdrive.pdf" target="_blank">manual</a>. It's printed right below the graph. I would also check the prime of the pump as someone else has stated.

Jay

 

[barbra]

I have a nearly identical setup on a 72g and water rips thru 1-1/2 line.

 

[Blackacid]

Thanks guys. based on what I see here, and the link provided to the other thread I'm thinking the biggest part of my problem lies with the intake. I'll start there and work my way around the loop.

 

[Blackacid]

Switched the drain pipe on the inside of the tank from 1" PVC to 2" PVC and that has made a big difference by itself. I'm going to change the 3/4" hose to 1" hose next to see how much more I get from that.

I'm trying to find a 1.5" to 3/4" connector, but I'll probably have to order the hose as I haven't seen any that size locally... except for rigid spa hose.