New book - 'Building a Better World in Your Backyard' - on Kickstarter (sponsored friend)
The water leaving our homes carries nutrients and value. It may also contain pathogens, and/or harsh chemicals and care should be taken with it. However, it is not a great risk compared to blackwater (sewage).
Redirecting the water we use for tasks such as showering allows us to reclaim some of that value to grow plants and recharge the water table. It may be necessary to choose our soaps and detergents more carefully, if we use the greywater for watering and fertilizing plants.