A discharge hose adapter adapts a standard marine thru hull fitting to a standard sanitation hose enabling discharge of a boat holding tank into a dump station. The adapter preferably includes a first component and a second component. The first end of the first component is frictionally engageable with the standard marine thru hull fitting, a first end of the second component is engageable with the second end of the first component, and a second end of the second component is engageable with the sanitation hose. The first component is preferably PVC injection molded plastic, and the second component is preferably compression molded rubber derived from vinyl monomers.