Your hot water tank if drained and blown out will not freeze, you can take out the relief valve if you wish and put a little anti freeze in the HW tank if you wish.
You sure do not need to put any in your fresh water tank as the water pump will pull the anti freeze in and fill the water lines. I would not empty them. just leave the anti freeze in for the winter. In the spring you can flush everthing out. The HW tank will be difficult to get the anti freeze entirely out of it, but it can be done. You should not need more than two gallons of anti-freeze to completely winterize,(depending on how large your 5ver is).
