[VWNate1]

Every region has differing mineral content in it's tap water, where I live it's so hard you can almost drive nails with it .

As mentioned, shopping around will net you $1 or less distilled water and it's foolish not to use it because you discover you should have used it by the scale that builds up in the cooling system out of sight....

I'm in a Desert clime so I use 60/40, the 40 % being coolant .