Closed Loop Plumbing

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New member
Dec 5, 2003
Looking for some help with plumbing a closed loop system.

I have a 180 gal acrylic tank that is 60" long, 30" side and 24" tall. It has two overflow chambers on each end, 8" square each. There is a "coast to coast" overflow 4" square across the whole back of the tank that flows into the overflow chambers.

I drilled holes for bulkheads for a 1" Durso standpipe for outflow to the sump in each of the overflow chambers and a 3/4" return that is piped through the overflow chamber and into the tank itself. Although I drilled each overflow for a return, I'm finding that one 3/4" return from my Iwaki 40RLT pump is sufficent. The second return is turned off at the ball valve. I had wanted to use an 1 1/4" outflow, but found that I could not get elbow of the standpipe into the overflow chamber. There is a 4" wide piece of acrylic on the top of the tank that reduces the entry to the 8" overflow. The 1" seem to work fine, so that's not an issue.

Now for the question - I have a Dolphin 3600 AmpMaster pump and a Haywood Electical Ball Valve to create a closed loop system that will change flow as the ball valve swivels from right to left sides (similar to Mike's setup). Both the pump and the ball valve have 1 1/2" input and returns. I have room in the overflow chambers for one more 1" bulkhead that I can to tie together with a 1 1/2" tee underneath the tank. But I'm concerned that I'll be pulling too much water through the overflow chambers and unless I get the standpipes exactly the same height, I'll "starve" either the closed loop system or water flowing into the sump.

The other method is to pull the input for the closed loop from just below the 4" square coast to coast.

The return from the Dolphin will go to 10 - 1/2" Loc Lines. I'm also not sure whether it's better to drill two 1 1/2" bulkheads in the back of the tank for the returns and have 1 1/2" to 1/2" tees inside the tank or to have the 1 1/2" to 1/2" tees outside the tank and drill for 10 1/2" bulkheads in the back of the tank (I'd also do this as close to the coast to coast as possible - just in case one leaks I want to try to minimize water loss). By having the 10 holes in the back of the tank, I'm taking up less tank real estate by not having a lot of visible plumbing along the back of the tank. I'm not too concerned about drilling ten holes - I've gotten fairly good at drilliing acrylic :).

Thanks for your input.


reefer addict
Aug 26, 2003
Portland, OR
Checkout Mikes tank and his CL. I would take the water for the closed loop midway down the tank through 2 2" BH's. Then use a 2" cross with three of them fitted with screens and the fourth to the BH. This will soften the "suction" of the pump. On the backside - use a reducer from 2" to 1.5" then to the pump. If installed correctly - you will have no leaks from the BH's.

One the return from the closed loop - you can mix it up, have 3-5 bh's on either side, use loc line and maybe even put in an eductor.

Also you might want to think of a spray bar near the bottom pointed toward the LR. To help keep the detritus out from under the rocks. :D

As Mike did, put the "T"'s outside


Why not close the coast to coast overflow off at the ends and drill the coast to coast for your loop inputs?

Alternately, put them in the corner overflows beneath the standpipe level. While you can starve your loop, there's no way to starve your standpipe, as all that return water has to go *somewhere*



Reef Keeper
Jul 5, 2003
Reefswimmer your set up sounds real solid. I would go up the back of the tank and stay 1 1/2 right up unti you go through the back wall, then reduce down to a 3/4 inch bulhead, thread by thread, this way you can screw in 3/4 locline. Going down to 1 inch prior will reduce the output of the pump by 40%