to get rid of the spots, put about half a cup of vinegar in your car wash bucket with you soap. Wash as usual. THere is nothing you can do to stop getting the spots, except not park by sprinklers. Even if you have a great coat of wax, the water will dry on the wax, and leave the calcium deposit there. Granted it is easier to get off from on top of wax, but it still sucks. Oh yeah, wax after you use the vinegar. Vinigar is an acid, and it will break down the calcium deposits, but it also eats wax.