The purity of the water that we drink and use to water our plants should be the concern of everyone. Your health and that of your plants can be diminished by water that loaded with chlorine, iron and other minerals, as well as bacteria and other nasty microscopic bugs.
When watering your plants the wise grower uses purified water whenever possible. Reverse osmosis systems and bulk filters are often attached to a fifty-gallon drum with a float value to insure a steady reserve of pure water. Using a TDS meter to test for Total Dissolved Solids growers can determine how many residual solids is still left in the water after filtering.
Pure water should test below 50ppm (parts per million) if you have hard water consider using a RO water purification system, or adjust your nutrient line to compensate.
After adding nutrients, the TDS will rise. For Hydroponics, readings between 800-1400 are typical, but for coco and perlite substrates, 600-1200 is more ideal.
For soilless/soil mixtures 300-600 should be your max, alternating between watering with nutrients and straight water to flush.
PH is also really important when feeding your plants. Ideally your water should be between 6-7 PH. Products like Ph UP and PH Down can help you stabilize you PH.
