Using grey water helps during droughts when watering gardens is restricted. Grey water is used household waste water, other than toilet water. It's usually water from doing dishes, laundry or leftover water from baths or showers. Although grey water doesn't have many long-term effects on plants, it does slightly modify the soil. The effects of grey water on plants depend on what's in the grey water, as well as the type of plant.
Effects on Soil
Grey water containing high amounts of laundry detergent can harm soil, causing sodium and toxicity problems. Products such as optical brighteners and detergents are made with petroleum based products which bio-degrade slowly and aren't good for soil, causing an adverse effect on growing plants. Also, grease from dishwater can accumulate in soils, hindering soil from absorbing water.
Effects on Plant pH
Generally, grey water is more alkaline than acid because it usually contains cleaning products. Therefore, using grey water containing alkaline-based chemical products can be damaging to acid-love plants such as Rhododendrons. Other plants craving acid include camellias, azaleas, begonias, gardenias, hydrangeas, magnolias, violas, primroses and impatiens. However, suitable pH can be somewhat maintained by alternating between grey water and alternative sources of water.
Effects on Plant Leaves
Because of the higher amount of alkaline or high pH, using grey water on plants can decrease important elements plants need. Iron is an elements that decreases as alkalinity increases. This shortage of iron can result in younger leaves of plants becoming a lighter green color or even almost white, although the veins remain dark green.
Effects on Metabolic Process of Plants
Grey water containing chlorine affects the metabolic process of plants. Chlorine is usually exhausted in the washing process, although some may be left in the grey water reaching plants. When chlorine is used in soils it can block normal metabolic processes, slowing down plant growth. Therefore, when using grey water from washing machines, consider laundry products that keep chlorine in water to a minimum. Also, have soils and plants kept at a low alkalinity.
Effects on Roots and Edible Plants
Grey water applied to either fine or medium-textured soils does not cause problems to a plant's roots. However, root damage can occur when it's applied to sandy soils with little organic matter. Also, overwatering and saturating soils with grey water for extended periods of time can result in damaging plant roots. Grey water shouldn't be used on plants with edible roots to protect the edible leaves from the threat of potential bacterial exposure. In fact, grey water shouldn't t be used on edible plants that are eaten either raw or undercooked.