It very much depends on your water company/utility district. I would start by calling them up and asking for the report. Unless you find it listed on their website, of course. Be specific about the ions you want the values for. Tell them you are not interested in a water quality report, which focuses more on pathogens and posions. It has always taken at least two separate communications when I try to get one.
You can go to the utility co and if they're nice they will have a printout for you. Ward lab also has a test ($20ish) that will give you exactly what you want. Note that your water will change with the seasons and if are going to use tap water you should get a reading and another reading 6 months later. Up to you though.
