Use only water from clothes washing, bathing or the bathroom sink. Do not use water that has come in contact with soiled diapers, meat or poultry, or anyone with an infectious disease. Plant specialists warn that gray water should not be used on vegetables, seedlings, container plants or acid-loving plants such as azaleas, begonias, and rhododendrons. Gray water should be rotated with fresh water to leach out any harmful build-up. Chlorine bleach may damage plants, especially if it touches the foliage.
Biodegradable soaps appear to have the least harmful effects.