And this is a problem that's VERY easy to prevent: a cupful of undiluted distilled white vinegar flushed through the system once a week. If you run out of white vinegar--4 gallons should last more than a year, though... rinse the salt water out of the hose DAILY with a quart or two of clean FRESH water. Had you done either one, there'd have been no need use up the Raritan hose cleaner (which also costs a lot more than vinegar).

But now that you have, muriatic (same thing as sulphuric) acid will dissolve your buildup without damage to the system. Mix up a 12% solution, being very careful to follow mixing and handling instructions. If you've let the buildup get bad enough to block the discharge line, it may require more than one "treatment" to dissolve it all completely.