Waste doesn't seem to be flushing from holding tank

I have the Valterra Hydroflush and it is a must-have even if there are bends in the pipe leading back to the tank. You might not get the direct impact blast of water in such a case but you will certainly have the ability to back-fill the tank for a good flushing. Of course that will not help with the white mountain problem that the OP has.

The Hydroflush will be as effctive as the H20 pressure where ever you are located.