From a recreational RV'ers perspective, I guess the black tank flush would be great if I were to get to use it. Most dump stations at the lakes in the central plains states have just a whip of a garden hose on a spring pole. There is no length to the garden hose nor a hose end on the hose itself. I believe the longer length gets run over too much. Stringing a hose 50' to the fresh water spigot doesn't make many friends at the Sunday dump station lines as most are in a hurry to get home. Ahhhhhhhh the perils of short stay camping!
Boy Howdy ... did I digress from the posters question or what?
On Edit ... Oh I know one shouldn't hook a flush hose to a fresh water spigot, but you see it all at the lakes ... that's why I don't use the fresh water spigots at the dump stations.