Your Silverpuppy is shutting down early because your distilled water has impurities/minerals in it. I had the same problem when I first bought the Silverpuppy. Had a bad batch of distilled water and it shut down early. I would recommend getting the meter sold on the silverpuppy site. A TDS meter is the second best choice, not very accurate though. That way you will know te purity of your water before you start. Optimally it should be 1ppm or less.