[ChuckS]

We use both air and anti freeze... blow out all lines and low points with HWH in bypass.. the water heater gets washed out and new anode rod installed

I like to follow up with antifreeze in the lines because..
.. water pump will still have some residual water in it and the antifreeze displaces water plus keeps seals wet and lubed
.. we pour a bit down the sinks and leave some in the toilet bowl to keep its seal lubed
.. each gray and black tank gets a little anti freeze down it to keep gate valves lubed

Also if you have fridge with ice maker you will need to drain its water line and then run air thru system and reset ice maker a few times so water solenoid valve will open and purge remaining water out of ice maker mechanism.

Don’t forget to blow air thru back tank flush receptacle is you use that...some water will remain 8n the anti siphon valve and it will freeze and crack