DIY Overflow Box

Materials :

Overflow Diagram


Construction Steps :

Inside Prefilter Box :

  1. The Specimen box has a "hanger side" that hangs perfectly on the edge of an aquarium. The small box will make a perfect inside prefilter box, just cut off its "hanger side", this will be used later for attaching the large box w/ the small box.
  2. Drill holes around the sides the small box. An inch below the top portion of the box will be a good section to drill. I used 3/8" dia. of drill bit to do this. These holes will be the water inlets to the box.
  3. Drill a small hole at the back end of the box. This where the nylon screw be used to secure the Outside Overflow box.
  4. The cut off "hanger side",this is a bent piece of plastic, should be flattened.You can heat its bent edges and push it on the flat surface to make it flat. Drill two holes on this so that the lower hole will perfectly attach its lower part to the small box w/ a nylon screw and bolt, and the upper hole will attach to the hanger side of the large box w/ a nylon screw and bolt. (Pls. see the attached diagram)


Outside Overflow Box (Large Box)

  1. Drill a hole at the bottom part of the box, the Barb Fitting should have a perfect fit in this hole. Silicon Glue the Barb Fitting in this, and it should be sealed water tight. Attach the 2" tube to barb fitting, this will keep the box filled w/ water and keep the siphon active. And to quiet down the gurgling noise of the water going to the intake, attach the "L" shape tube on top of the 2" tube. This inlet will will lessen the noise of air being sucked down inside the tube.
  2. Test fit this box w/ the small box so that the water inlets are leveled to the aquarium water level. Mark up the area where a hole will be drilled on the "hanger side" that will perfectly attach to the small box w/ the flattened plastic.
  3. Secure the screws and bolts of the small box w/ the large box. You can apply some Silicon Glue on the surfaces for a firm attachment.

Siphon Tube :

  1. Trim the tube appropriately so that both ends of will sit an inch off from the bottom part of the boxes.
  2. Drill a small hole ( to fit in an airline tubing connector) on the bent part of the U-tube. Attach the airline tubing connector w/ Silicon Glue on this hole (make sure it's air/water tight). Attach a length of airline tubing on the connector w/ Silicon Glue. This airline tubing attachment will be used to start the siphon by sucking the air out of the tube. If you don't like the taste of saltwater, you can use a big syrenge (w/o the needle) and attach the airline tubing to its nozzle and suction out the air w/ a single stroke and put a binder clip on the airline to close it.

I suggest to test this contraption to check for leaks or weakness on the attachments, before putting it to the aquarium. I tested mine by running this system w/ my return pump in a bucket of water by returning the water to the inside prefilter box. This is also a good test for the U-tube siphon rate and the the rate of the return pump. This is where I found out the need to attach a control valve (I got this from my Rio pump) to control the rate of flow from the Overflow box to the sump. Overall I am satisfied w/ the flow of rate of water being dumped in and pulled out from my 20H aquarium, it gives a consistent counter-clockwise (Charles Delbeek) current of water.

Other Diy Overflow Projects Information

Need more answers?

Check these related articles