I have you involved, What would you suggest to clean the hoses from and to the holding tank. I have a manual hand pump for overboard discharge, a deck fitting for shore side pump-out stations and a 3 way valve. Would you suggest pouring some acid in the holding tank and pumping it out with the hand pump? If so, would it be the same concentration as if in the head alone? I would think it would be but I'm not sure how a holding tank might react with all that bubbling going on.