Problem getting rid of waste water.

greylag

Only had our Swift motorhome for a few months and still getting everything just the way we want.  The waste water outlet tap is just too low to get our ex caravan container under and it is quite a palaver to do away with the water.  I have just noticed that
the tap has an internal screw thread, has anyone got any ideas as to what type of fitting goes into it?

Here's hoping.