[JRTJH]

Galley gray tanks typically are plumbed with 1.5" slide valves and drain pipe, connecting to the 3" sewer outlet on the trailer. The black tank is plumbed with 3" valve and 3" sewer line. With the 3" fittings, there's barely enough flow force to empty the black tank and almost always needs to be flushed to empty the remaining solid contents. There's simply not enough flow force through the 1.5" valve to flush the solids from a garbage disposal out of the tank. I'd guess that in a couple weeks of heavy use, you'll be taking the disposal out and working (or hiring someone else) to try to clean your galley tank to stop that awful odor that comes up the sink every time you pull the plug and drain the dish water.