Domestic water supply tends to be very hard in this area
it is the lime in it that leaves the marks when drying
Rain water tends to be soft and won't leave the marks, but I'm sure Taylor will tell you it contains impurities from the atmosphere
I've often washed the car in the rain then rinsed and the rain water has then washed the domestic water away and guess what
no water marks
Can always wax when dry
"Life's too short not to!!"