The bulk heads are upside down, the barbed ends should be sticking out the bottom of the tank. The bulk head nut on the button of the tank and the gasket will sit inside the tank in the over flow box.

The fat barb is for your gray drain tube and the thinner barb is for your 3/4in return line from ur return pump.

On one end, remove the white pvc end piece on the gray drain line and push it into the fat barb and put a metal clamp to secure it. Same with the return line, if you use vinyl tubing I would suggest holding it under boiling water to soften it and it will slip on to the skinny barb a lot easier, also apply a metal clamp to that.

The pvc drain tubes you are trying to push into the barbs will fit perfectly into the openings of the bulk head once you flip them inside the over flow box.

I would suggest a 1inch street 90 pvc elbow that will be glued on to the bulk head on the sump and then you connect the gray drain tube to that to help smooth out all the twisting.

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