We actually get our water from the Sierra's out of the outingdale water system and lakes just above El Dorado Hills. After reading your post I figured I should call the Water district and find out what their levels are. They said that we have incredibly low mineral levels and that they keep the water at CH 20 and PH 80-90. He said he said that this has been the case for a very long time and that its very safe and that although he doesn't work with pools he does recommend that I stay far away from pool supply stores. Which I though was funny!