I guess you could open the upper hatch at the wardroom and feed the grapple
and then hose in there.
And pass down some Dairy Cream Sponges while you are at it!
I suppose that if a tanker was available (and you didn't bother about the oil) then the limits for endurance would depend upon the capacity of the elsan toilet (which is just a bucket with a seat on), although I suppose it could be baled out and the contents poured down the flare shoot. As an aside, the elsan had to be "cling-filmed" before any air-display to prevent spillage.