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Greywater is the wastewater that comes from the laundry, kitchen, bathroom faucets, baths, and showers. Greywater, if properly collected and stored, can be safely re-used, thereby reducing fresh water consumption. Graywater is distinguished from "black water", which is wastewater from toilets, kitchen sinks and dishwashers, and should never be reused in the home as there are possibilities of contamination by bacteria, viruses, and other pathogens.


Why should I be aware of this?

Greywater reuse is a part of the fundamental solution to many ecological problems. Grey water can replace fresh water for irrigation. Residential water use is almost evenly split between indoor and outdoor. All except toilet water could be recycled outdoors, achieving the same result. It's a waste to irrigate with great quantities of drinking water when plants thrive on used water containing small bits of compost. The benefits of grey water recycling include:

  • Lower fresh water use
  • Less strain on failing septic tank or treatment plant
  • Greywater treatment in topsoil is highly effective
  • Ability to build in areas unsuitable for conventional treatment
  • Less energy and chemical use
  • Ground water recharge
  • Plant growth
  • Reclamation of otherwise wasted nutrients

Greywater and environment

The potential environmental impact of greywater on the topsoil is not clearly known as no long-term study has been conducted so far. As a result, there are few regulations on the books that govern the use of recycled grey water. If you decide to install a greywater recycling system, your household should use biodegradable, organic soaps and detergents to minimize the impact on the environment.

All about greywater

It is estimated that 50 to 80% of all wastewater a residence generates is grey water, which can be reused in irrigation of the landscaping. Greywater treatment is a specialized process and requires expert installation and maintenance. Different methods of treating greywater are available, and as the technology improves, more will be more options to choose from.

It is true that greywater gets contaminated with organic materials and pathogens, bacteria and virus because of the chemical cleaning products we use. But if properly handled it can be safely re-used to water vegetation in the garden, because the nutrients in the cleaning products are readily absorbed by the vegetation being watered. The pathogens are digested by naturally occurring organisms in the soil such as bacteria and worms in the garden irrigation areas.

Flush toilet water is not used in the greywater system but is sanitized in a separate containment area and then used in gardens and lawns.

The Earthship, a futuristic dwelling unit made from local recycled materials, is one of the few residential buildings with a water recycling module that utilizes greywater an unprecedented four times.


Using a greywater system offers multiple benefits including:

  • Saving money on water bill
  • Reducing your fresh water usage
  • Reducing wear and tear on septic tank
  • Decreasing the amount of chemicals used to treat the water you garden
  • Reclaiming nutrients in the water to re-invigorate the soil
  • Increasing the level of clean, local ground water

Two types of systems

Greywater systems come in two varieties:

  • gravity fed manual systems,
  • packaged, stand alone systems.

The manual system uses gravity to send the greywater to the areas where it is needed without electricity or pumps. Packaged systems require electricity and can be installed indoors.

Another way to reclaim otherwise wasted water is to use catchwater systems in which the water that accumulates on your roof is channeled through silt catches and fed into cisterns. The cisterns then pump the water to a filter. The filters clean the water for consumption and cleaning use, then the system pumps it back into your home.

90 degrees

Use of greywater on landscape not only conserves potable water, but such water may actually be better for plants. Ofter greywater produces more vigorous vegetation as it contains detergents with nitrogen or phosphorus which are plant nutrients. It may also contain sodium and chloride which can be harmful to some sensitive species.


  • What is Grey Water?
  • Greywater Recycling and Irrigation Systems
  • How to Reduce Your Water Bill Using Grey Water Systems