Why Is Drinking Water Still Used For Flushing Toilets?

Posted on Dec 11, 2023 at 8:02 am by Oliver C

As the demand for more responsible and sustainable water use increases, French regulations still limit the use of gray water – domestic wastewater from showers, sinks, and washing machines. However, solutions exist to develop their potential while respecting health requirements. We explore the different possibilities offered by the use of gray water.

The current state of gray water use in France

In France, the National Agency for Food Safety (ANSES) only allows the use of gray water in water scarcity contexts. Gray water must be treated before being used for three potential purposes: toilet flushing, watering green spaces, and cleaning certain outdoor surfaces under certain conditions. However, there is very little regulatory framework for gray water, especially in residential buildings. Therefore, its use remains prohibited except as a case-by-case experiment.

The challenges to be overcome for widespread gray water use

The caution of health authorities regarding gray water is explained by the fear that these liquids, which remain non-potable even after treatment, may contaminate the water network intended for human consumption. However, each risk associated with the use of gray water now has technical solutions to ensure health safety.


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Innovative projects in gray water management

Several key projects in France demonstrate the potential of gray water for better water management:

  • The Chalet of the Tête d’Or Park in Lyon: a membrane filtration system should allow the reuse of rainwater and gray water for sanitary facilities, laundries, and irrigation systems in the park.
  • Bordeaux and Ivry: researchers are participating in the installation of gray water treatment systems using phytoremediation (water filtration through plants) in residential buildings under construction.

Through these examples, it is possible to demonstrate that the use of gray water can be safely extended to other purposes, especially in residential buildings.

The opportunities offered by gray water use

In buildings equipped with gray water treatment systems, up to 60% of the water used can be recovered and treated. However, the authorized uses (e.g., toilet flushing) are too limited compared to the available water resources. According to the Ministry of Ecological Transition, decrees should be issued to facilitate the widespread adoption of gray water reuse in housing.

Smart water use to save resources

In addition to integrating gray water treatment systems, it is possible to optimize water consumption through simple and ingenious solutions:

  • Dual plumbing: this method involves distinguishing pipes carrying gray water from those connected to the potable water supply.
  • Combined sink-toilet bowl devices: inspired by Japanese models, these installations allow the use of sink water for toilet flushing, thus saving water.
  • Connecting washing machines, showers, or sinks to toilet flushes: this solution also saves water without the need for complex systems.

In conclusion, the use of gray water represents significant potential for more sustainable and responsible water management in France. Thanks to innovative projects and available technical solutions, it is time to accelerate the widespread adoption of gray water reuse in housing while respecting health requirements.


About Oliver C

Oliver, a dedicated and passionate individual, has been a consistent contributor to various projects. With his unwavering commitment and exceptional skills, he has proven to be an invaluable asset. Oliver's ability to think outside the box and find innovative solutions sets him apart. His positive attitude and willingness to go the extra mile make him a true team player. Oliver's determination and drive to succeed inspire those around him. With his remarkable work ethic and strong attention to detail, he consistently delivers outstanding results. Oliver's future is bright, and his potential is limitless.

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