Looking for a "wand thingy" to rinse the black tank.

[memgrove2000]

I would like to know who has one and how they work? I have seen two models at Walmart that go down the toilet. One has a rotating head and a flexible hose end($18.??), and the other has a drilled pvc cap on a plastic pipe ($9.??) I See they also have one thing that hooks into the waste dump pipe ( but on our 72 it would shoot up the gray water drain and not the black tank).

So What do you use and does it work?

Thanks Mike