What more explanation are you wanting? Thanks to that post, I found a few different heavy metal tests on Amazon [0] for a general indication of quality. It also looks like I could also ask one of quite a few local labs if I trusted them and wanted a more in depth set of results [1].

[0] http://www.amazon.com/Sensafe-480309-SenSafe-Heavy-Metals/dp...

[1] https://www.calwater.com/waterquality/water-quality-testing-...