[JRTJH]

Please explain what you mean by "the toilet clogged".... There's nothing but a straight 3" pipe from the ball valve in the toilet to the black tank. If it's "plugged" a simple broom handle should push the offending "plug" on down the pipe.... If the black tank is "plugged" what part? The dump valve? the "pyramid of poo" under the toilet pipe? the actual black tank? the tank vent pipe that goes to the ceiling?

More information please, so far there isn't enough information to even know what's "plugged".