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Grey Water Recycling


What is Grey Water?

Grey water (also known as sullage) is non-industrial wastewater from domestic sources such as washing dishes, laundry and bathing. Greywater differs from blackwater in the amount and composition of its chemical and biological contaminants (from feces or toxic chemicals). Greywater gets its name from its cloudy appearance and from its status as being neither fresh (white water from groundwater or potable water), nor heavily polluted (blackwater).

What is Black Water?

Blackwater is a term used to describe water containing high levels of organic waste such as fecal matter and urine. It is also known as brown water, foul water, or sewage.

What is Potable Water?

It is important, since we are talking about types of water, to recognize and understand the term "potable".  Potable water basically refers to municipally provided water that meets the applicable municipal/regional safety standards for quality and is considered safe for drinking.  Although there are many sources of water which people may drink it doesn't necessarily mean that these water sources meet specific quality standards and are thus considered potable.

What is Grey Water Recycling?

Grey water recycling is a process in which wash water is taken from sources such as the tub, shower, and optionally the washing machine, filtered and treated, and re-used again for the flushing of toilets.  In some areas grey water is also acceptable for use in irrigation for watering of plants and flowers.

pie-chart.jpgMore about Grey Water Recycling

Based on statistics about 70% of all water used in the home would be classified as grey water.  There are some considerations, however, that should be made when considering using grey water recycling.  First and foremost always consult with your local plumbing officials and appropriate regulatory representatives to ensure that you use grey water in a safe, and building code compliant manner.  When choosing sources for grey water recycling it is important to consider a few additional items:

Grey water must be treated if it is to be stored for any period of time to avoid further contamination and to control odor as the contaminants in the water begin to break down.  Chlorine is the most common form of treatment used to kill bacteria in a grey water recycling application as it has residual effect (excess chlorine or free chlorine).  Free chlorine will remain in the water for a time and provide treatment longer than point of contact type treatments like UV.  

In Ontario, Canada we are fortunate to have progressive and conservation focused inspectors and regulatory officials that understand the importance of conservation and efficiency.  As a result the Ontario Building Code supports the use of grey water for flushing of toilets.