Using bath water to water plants is one way to recycle water that would otherwise go down the drain. In times of drought, to conserve water or simply if you're trying to cut your water bill, you can save water left over from baths and use it to water your house plants. Plants won't be harmed by the minimal quantities of soap usually found in bath water. Don't use bath water on any edible plants, though, since bath water may contain harmful bacteria you don't want to ingest.
Leave the plug in the tub after you finish your bath. Allow the water to cool.
Fill a watering can or bucket from the tub. Use this container to water your plants.
Check local regulations before using bath water on any plants outside of the house. Many states and municipalities prohibit the use of bath water (otherwise known as gray water) on lawns or garden plants.