Water from bathroom sinks, bathtubs, showers, and washing machines is classified as greywater and, depending on local and state regulations, can be diverted to irrigate landscaping. The water that dishwashers and kitchen sinks produce, on the other hand, can be contaminated with food and can’t be used in greywater systems. Toilet water is off-limits as well. A simple, low-tech greywater system can be professionally built for $1,000 to $2,000 by installing a three-way valve to funnel water from a washing machine to a hose or pipe that disperses it to the landscaping.