Mr. Newell Owner,

We have a 2000 Marathon "H"3-45. Our tank capacities are as follows.
Fresh tank=186 gallons plus 21 in the hot water heaters
Grey tank=86 gallons
Black tank=68 gallons
We have 2 separate dump vavles, one for grey and one for black. These valves join a central exit where the sewer hose attaches.

Another coach we know, a 2002 Marathon "H"3-45 has the same system as ours, but also has a macerator that diverts grey/black water thru a chopper/blender and sends the fluid out a separate port where a garden hose may attach. This macerator pumps the mess thru the hose and into where ever you put the hose.