For health reasons, gray water should not be sprayed into the air or applied directly to plant materials. Apply gray water at or slightly below the soil surface under the plants. Surface broadcasting by soaker hoses or a similar trickle system is recommended. Apply the gray water slow enough to prevent runoff. Excess applications can also result in soil erosion and contamination of existing water supplies.
Gray water has few long-term effects on soil.
Gray water slightly modifies soil-organism populations but causes no pest problems. Continued application of gray water to the same area or plants should be avoided. Apply the water to a different location in the landscape at each application to reduce potential problems. Robert Nuss is a horticulturist at Penn State. He coordinates all extension horticulture programs.