Q&D way to test for water purity:
Get your ohm meter and get a container of distilled water.Set up two (or more) glass or plastic (glass preferred) trays for your testing waters.
At room temperature and right away (to prevent carbon dioxide, from the air, contaminating the water) pour your distilled water into one of the trays.
Find the distance you need to hold your probes apart to get a reading of 500,000 ohms. Do the same test in whatever water you choose, to see if the water is (or even close) to 500,000 ohms (or better is preferred).Some helpful links:http://www.aquaread.com/need-help/what-are-you-measuring/resistivity/http://www.labmanager.com/white-papers-and-application-notes/2010/05/resistivity-conductivity-measurement-of-purified-water#.Wdt3_EyZNE4https://sciencing.com/measure-conductivity-water-multimeter-8523350.htmlhttps://www.youtube.com/watch?v=ORxy-m3vcxc