Its just about time fire up the boiler again. Last year when I was gone for a week my lines to the house froze. I got them thaws after some work but don't want that to happen again. Can I use regular automotive anti freeze, I can get it in bulk barrels, so it is some what reasonable My system probably holds 80 gallons and is an open system. Or should I just buy boiler antifreeze. thanks for the help. Jim