Closed Loop Help

[Kennetht]

I'm attempting to setup a closed loop on my system, and I'm having some problems. I'm using a Mag 12 as the pump, and everyone says to double the size of the pipe. The mag has 3/4" inlet & outlet, so 1-1/2" should be the correct size for the pipe. I hooked everything up last night, but it was like the pump couldn't pull enough water into it, to keep it running correctly. The tank is a 135G, and will have 2 oulets coming from a SCWD back to the tank. The SCWD has been dremeled out to make the openings bigger to allow more flow. If I set the pump behind the tank, and build a shelf for it, I can pretty much put it anywhere to get the correct flow. I was thinking of putting it even with the tank bottom, which would give it a 2' head. Would this be ok, or should I move the pump closer to the top? Also, on the intake side, should I use a piece of pipe with holes drilled in it, or use the screens for bulkheads? I appreciate any and all help, as this is about to drive me crazy!!!!

 

[fishdoc11]

You won't have any head with a CL except for what is caused by pipe diameter. It really doesn't matter whether you use the drilled pipe or a screen. Not sure why the Mag would not pull consistantly unless maybe you have'nt added a primer port to the U tube and the pump isn't primed.
Chris

 

[cee]

Your head pressure will be dominated by the SCWD, not the diameter of the inlet tubing. I don't understand what you mean by "the pump couldn't pull enough water into it, to keep it running correctly". Perhaps you have cavitation caused by using such a large diameter inlet pipe which has to neck down to the inlet diameter of the pump? HTH.

Dave

 

[jdieck]

The pump must be below the water level not on top of the tank for it to properly function (Needs flooded inlet).
It does not matter much how deep below the water level, the bottom level of the tank will be OK.

 

[imsqueak]

Is the feed "thru the tank" or over the top? I basically have 2 CL if you count the chiller. The chiller is fed over the side and I used like 1' of 1" pipe which I drilled about 50 3/8" holes and but a piece of screen over the bottom. Before the holes the screen would clog too often and snails would get on and restrict flow. My real CL is a 4300gph fed by 2" pvc. I had to use a cross with strainer caps and drill 100 holes in the cross because the 3 2" openings would still trap fish to the intake. The chiller is a total PITA to restart after I pull the pump or clean the chiller. I insert airline tubing down the pipe and suck out air for about 10 minutes. No other way to prime it the way I have it set up. The big CL has a screw out fitting at the top that I can pour water down to fill the feed.

I suspect cavitation due to not filling priming it. Try the airline trick if need be.