Reuse the water you use for cooking food such as corn and pasta. Do not use salter water, though as salt will damage the plants. let the water cool before pouring it on the plants.
Reuse your pet's drinking water.
You can use the water that you bathe in and the water that you wash dishes with to water the plants. The soap will not harm the plants.
Water from a dehumidifier can also be used to water plants.
Set out containers to catch any rainwater. Also, divert water coming down the rain spout towards a tree or shrubs.
Practice Effective Watering Habits
Do not water with an oscillating sprinkler. They waste water and often only water the foliage and do not allow the water to penetrate to the roots.
Do not spray plants with your thumb over the end of the hose for the same reason listed above.
Water SLOWLY and deeply. It is best to water plants by placing a hose at the base of the plant and running the water at a slow trickle. It is better to water plants less often, with more water, than to water daily with just a shallow watering. Some hoses have a smaller diameter, which allows for healthier watering techniques.
Soaker hoses are great and use substantially less water than any other watering practice. However, most people do not let them run long enough; they should run for at least six hours.
It is best to water early in the morning. The plants will use the water to survive the heat of the day and less water will be wasted through evaporation.
Another great water conservation tool is a portable drip-irrigation system, such as the TreeGator. There is virtually zero water loss! It is very simple, and easy, to use. Just place the bag on the tree, or shrub, fill with water, and forget it.