Once the drain is installed it's a simple matter of connecting a rubber Fernco coupler to the connect another section of pipe to the floor followed by a three in inch elbow. Then a section of 3 inch pipe (all 3 inch pipe) runs along the floor to a knife gate valve to which is also connected on each end with a Fernco coupler.
Next comes a t and a vertical stand pipe with a vinyl hose that is directed to a drain or waste line.
Twice a day I pull the knife gate handle and this flushes waste laden water from the center drain and around the center drain. I vinyl hose on the other side of the vertical stand pipe turns dark momentarily with waste.
Shower drain installed in the bottom of a plastic tank. (Previously used a washer shaped piece of heavy plastic as a retainer ring.
Picture showing sequence of shower drain glued to PVC pipe, Uniseal, and Fernco coupler. Tank not shown. 
The drain, PVC pipe couplers, knife gate valve, fittings, and standpipe minus the tank. 
Contrary to what you may think the stand pipe needs to be higher than the water level of the tank if you use it to purge waste products. The forceful surge up the standpipe to briefly remove solids causes it to rise higher than the water level. Learned this the hard way after I got wet the first time!
Obviously the the stand pipe has to be in a vertical position.
I prefer the fernco couplers vs. gluing fitting together as it allows me to take things apart easily for relocation and cleaning when I temporarily shut down a system.
Here's a close up of where reducers and a barbed fitting were attached to install the vinyl hose as a waste line.
Note: A knife valve developed a chronic leak at one the high schools I installed a system at. I added an additional ball valve downstream of the knife gate valve inline of the vinyl hose to preclude losing water from the system. This was cheaper than purchasing another knife valve, and the problem of disconnecting even temporarily a system full of fish and water to install a new one! Can you imagine the water rushing out of a 3 inch pipe while frantically trying to slide on a fernco cooler and tightening it?!
