102: Soaps & Other Contaminants
“Soaps and Detergents help with Irrigation, because they decrease the surface tension of water, making it easier for water to move within soil.”
“Liquid soaps are better than powders and bar soaps because they do not contain fillers (best avoided for soils) and fats (more difficult to filter).”
“Only one type of soap (Boron / Borax) must not be used, because it is toxic to plant life.”
Soaps help with Irrigation, if spread over a large area
Surfactants in soap and detergents help irrigation within soil by reducing water surface tension, making it easier for water to move within the soil. However if a large amount of soapy water is concentrated in a few holes in the ground, this could result in toxic buildup over time. This is why reservations have been raised about concentrated irrigation methods such as Laundry to Landscape and Branched Drain gravity systems that have a limited number of mulch basins as outlet locations.
Because IrriGRAY uses a large number of sub surface emitters covering thousands of square feet, any soap is dispersed over a very large area and therefore does not create toxicity issues. It is even possible to use aggressive agents such as chlorine e.g. Chlorox without issue.
If you are concerned about soap in the environment, we recommend first considering the dangers of soap and detergent use inside the home. For example, instead of using very strong shower cleaners that produce potentially harmful vapors, trial some citrus oil based cleaners that do almost as good a job but present far less personal safety risk.
Liquid vs Powder Laundry Detergent
Powdered laundry detergent usually has at least 50% filler content, and of high sodium levels. Therefore Liquid detergents are preferred. Note that some manufacturers are claiming their products to be 'green' simply because the detergent container is made from recycled plastic, rather than any particular 'green' effect from the active ingredients.
Bar Soap (Hand Basin and Shower Use)
In the Graywater Collection section of this course, we discuss avoiding hand basin graywater where possible, but some locations such as Tucson, AZ have mandated the use of this water. Bar Soap, especially cheaper products have very high fat content. These soaps should be avoided because they can result in a layer of fat building up on top of or within the soil. Fats also build up quickly on the filter requiring more frequent flushing.
Hand Soaps / Shower Shampoos and Gels are preferable for the environment and the filter alike!
Boron based Soaps (e.g. Borax or similar)
Boron can be toxic to plant life in medium - large quantities and should be avoided.
Like cheaper bar soaps, Fabric Softeners can contain significant levels of fat, therefore creating soil and filter issues. We recommend using dryer sheets instead of liquid fabric softener.