Using plain water in a blow off jug isn't the same as in an airlock where the water has less distance to travel in an airlock vs a hose in a jug. You can boil it all you want before adding it,but as it sits & cools,nasties can get through the holes in the airlock cap. One suck back & you could be infected. I can get a pint of cheap vodka at BP for $2.58. No foam,no live nasties,no evaporation.