I bypassed the hot water heater and pumped the pink anti throughout the entire fresh water system. I would rather not put the anti in the hot water heater as I've been doing the last two years. When I bought the boat, the fellow from the dealer suggested I isolate the heater then pump the anti directly into it until pink comes out the cold water hose. This causes a problem in the spring. Trying to empty all the anti from the heater is a real pain. I gather from this forum all I really need to do is isolate the heater and then drain the hot water heater. This year, I did this and drained most of the fresh water in the tank. My concern is I cannot seem to drain all the water from the tank. I tried blowing into the hot water hose and did get water expelling from the cold water hose. However, this was exhausting and in no way is the heater completely drained. Do I need to be concerned with the residual amount of fresh water in the tank? Winters here are brutal.