Ward Labs is very reputable and will do a great job on your water test.
I know my water changes based on time of the year. In the spring, it's all snow melt and rain coming down from the Cascade Mts, so there's almost no mineral content. In the summer and fall, the mineral content picks up noticeably because the water picks up more minerals from the aquifer (a lot less channeling - similar to a slow vs. fast mash runoff).
HTH-