Keeping houseplants happy and thriving in your home is a great way to improve the air quality of your home. One simple way to water them is to use secondary water sources. It's simple: About to pour half-empty glasses of water down the drain after dinner? Give them to your plants instead. About to enjoy a hot bath, but waiting for the water to heat up? Fill a watering can in the tub and give it to your plants. Ice cubes and cooled water from the teapot are other easy sources of hydration for your plants.