Plants need two basic things: water and light. The best water for your plants is free of impurities such as minerals and chemicals.
Pouring water straight from the tap:
The advantage of using water from the tap is that it’s cheap and readily available. For many people, straight from the tap is fine. Make sure it’s not too hot or cold; room temperature is just right. Others have tap water loaded with minerals or chemicals that can harm plants. They can use tap water as well, as long as they take some simple precautions.
Chlorine, which some municipalities use to kill disease-causing microorganisms, is bad for plants. Chlorine is a gas that evaporates out of water easily, so if you smell chlorine, let the water sit for 24 hours before using it on your plants. Use clean, empty milk jugs or soda bottles to hold the water while it “breathes.”
Some areas have “hard” water that has excessive amounts of minerals (mostly magnesium and calcium). These minerals are bad for your plants, so you shouldn’t use hard water directly on them. If you have hard water, be sure to filter it with an activated carbon-type filter.
Some would use bottled water for their houseplants, although we strongly don’t suggest this. It is not only bad for the environment, but will end up being extremely expensive. Instead, filter your tap water using a water filtration system, which provides chlorine free water that is softened and rich of healthy minerals or collect natural water with a rainwater harvester.
Wherever you get your water, use it wisely. Don’t over-water your houseplants. Far more houseplants are killed by over-watering than under-watering. Never water your plants without checking first to see if they need it. Stick your finger about an inch down in the soil. Unless that entire inch of soil is dry, don’t water.
Read more: The Effects of Tap Water on Plants