As you run the AF through the system some does end up in the BW tank.
Given the size of the tank and relatively small amount of water there is tons of room for the ice to expand with no damage, just be sure to drain any water near the dump valve.
You could dump more down the toilet if you want.
2016 F350 6.7L LB CC Reese 28K 2014 Chaparral Lite 266sab
"Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety." 2014 19 days camping 2015 17 days camping201620 days camping