Stupid question, but just want to be sure. I'm going to flush my rad, but since I live outside the city the garden hose water is hard. I know enough to not use hard water to mix w/ my antifreeze, but is it o.k. to flush the system with hard water??

 

I would keep flushing with distilled water.....remember, you can't totally drain the cooling system, so a certain amount of water will stay in the system.