I was wondering if there is a special way to winterize the Black Tank Flush line. I have a leak in mine, and the dealer said it might have froze. When I winterized the RV I pumped anit freeze through all the faucets, washer and dryer,shower in the bathroom, toilet, and outside shower. Is this flush line separate from the rest of the water system and if so how do you winterize it if it has to be winterized. I do not want this to happen again, if indeed it did freeze. I have winterized other RV's for the past five years and never had this happen.