The drain pipe which connects to an external stand pipe. The Fernco rubber coupler on the right connects to the section of PVC coming down from the center drain. The Fernco rubber coupler on the left connects to the 't' assembly in the second picture,which is where the external stand pipe rests inside. Note the 't' is 4 inch vs. the rest of the drain pipe which is 3 inches.
The 4 inch pipe is inserted into the 4 inch 't'. It's not glued.
The purpose of the Fernco couplers is for easy disassembly of the system if you want to move it. Also cleaning of pipes, hoses, etc. if the system is shut down.
The following is the drain pipe and 4 inch 't' in service. You can't see where it runs under the tank and up the center train due to the clarifer tank to the left.
Note the drain line on the floor that is connected to the rear of the 't'. Twice a day an hour after feeding the gate valve in front of the 't' is pulled up for about 5 seconds and then closed, which violently pulls out about 2 gallons of water to the top of the 't.' This removes and dislodges solids in and around the center drain. Once the purged water and solids are purged the ball valve the behind the 't' is opened. Then the external stand pipe is scoured out with a garden hose and nozzle.
The hose that comes out of the 't' that connects to a barb fitting. Note the ball valve.
