MrHello,
Basically there is a hole cut out in the center of the fish tank (4 inch hole for 3 inch Uniseal) The Uniseal takes the place of a more expensive bulkhead fitting.
A piece of 3 inch PVC with a shower drain inserted and glued into a section of 3 inch PVC pipe and a plastic washer to keep it from pulling through the Uniseal and tank, goes down from the center to an elbow via a rubber coupling.
Here's is the shower drain without the grading cut out.
Here the grading has been cut out:
Here are the three components separated:
On top of the shower drain in the center of the tank is a flat plastic plate attached with stainless steel screws to keep the fish in (1/2 inch gap), but also allow water to flow down to the clarifer tank (plastic drum).
Here's a membrane diffuser attached to the flat plate, which btw, also prevents a vortex from forming as the water goes dowh the drain, which is advantageous. The diffuser added oxygen and is supposed to help in self cleaning of the tank.
Here's a view under the tank to show the connections.
From there the 3 inch PVC drain pipe goes along the floor to a gate valve and another rubber coupling. When draining the clarifier tank to get rid of solids I close the gate valve and cap the siphon tube to prevent draining the tank. (This is the yellow perch tank).
Another short piece of PVC connects to a 't' which connects to a plastic drum on the vertical part of the 't', and the rear edge of the 't' goes to a drain hose and ball valve to close or open the hose.
Water is pulled up through filter material in the barrel to both the spray bar and the RBC tank via a small pump sitting on top of the filter material in the barrel, which is adjusted with a ball valve. The overflow goes back to the fish tank. The water going to the RBC tank drops in center paddles which turn the RBC.
