Funfinder could not make it easier. I do my entire 189FBS with ONE gallon of antifreeze. You should not only have a hotwater heater bypass, but you should have another tube with an inline valve. With all of these valves, when they are in line with the waterline they are open. When they are turned so they are postioned across the waterline they are closed. This small length of tubing that appears to go nowhere is utilized to put directly into your antifreeze container. While someone holds the container to ensure it does not spill over, you turn your demand pump on, go to the furthest tap from the watertank, which is usually the outside shower, turn on both hot and cold water taps until you see pink. Then go to each tap in your trailer, furthest to the nearest and do the same thing, including your shower and your toilet. Run enough so antifreeze rests in each trap. As mentioned, I get by with a one gallon bottle. You may need two. You do not need to dump antifreeze into your water tank. You will need to ensure that you have the taps turned the correct way to bypass your hotwater tank. Remember the rule for the direction of the valve tap. If they are turned the direction of the water line, it means they are open. Another critical note. If you use the short length of hose to evacuate the antifreeze from its container into your system, make sure you turn that valve to the OFF position when you are through. Otherwise, your demand pump will not work because it will not be able to build up pressure in the system when you are ready to re-use the trailer.