I have the valve on the pump inlet side that switches the intake to a tube I put in a jug of antifreeze. Works great. I worry about the water in the pipe between the tank and the pump. There should be another valve to let air in and make that water fall into the tank. And I worry about a little water being left in the bottom of the tank and the drain tap - could that tap burst when the water freezes? So after draining the tank I put a clear tube on the drain and let a little antifreeze flow in to fill the tap. Or just pour a Liter of it in the water fill. After a little flushing in the spring there is no pink tinge to the water and the dog is okay drinking it. I haven't drunk any myself because I don't sterilize - I hate the taste of bleach.
It seems to me those of you who put bleach into the tank to sterilize the system will have a worse taste problem than a tiny bit of antifreeze would cause. At $1.50 a gallon, I would just pour it into the tank, too. But my pump doesn't self prime unless the tank is full, so I would have to use that valve behind the pump to prime it anyway.