Can I reuse shower or washing-up water in my French garden during drought?

Reader Question: I live in an area where there are restrictions on using tap water in my garden, and I hate to see my plants and vegetable patch wither. Is it possible to use water from inside the house, such as after the washing-up, to water them, or is it too dangerous? 

As France’s historic 2026 drought continues, limits on using tap water to water gardens and plants are now in place in the majority of departments. 

Many people are therefore considering using waste water in place of tap water for daily activities, however this is not always possible. 

Waste water collected from showering, bathing, bathroom sinks and washing machines is known as eaux grises (greywater) and comes with its own set of restrictions.  

Do not be disheartened though. It is certainly possible to capture and reuse eaux grises and in fact in an age of increasing water shortage the French government is encouraging exactly this.  

Note that water from the kitchen sink or dishwasher is classified as a different type of greywater (eaux grises issues des cuisines) and is more restricted.

Water used for washing-up by hand in a sink can only be used for limited purposes that do not include watering vegetable gardens, and requires stricter authorisation procedures.

However, water used from the kitchen tap that does not go down the sink – i.e, collected water used for rinsing or boiling foods – can be reused in certain situations.

Restrictions on greywater use are different from other water sources such as rainwater or well- and river-water, which all have their own rules and restrictions. 

You can read about rainwater harvesting and rules for well- and river-water in our article here.

Note that eaux noires or eaux vannes (blackwater) coming from toilets or sewage – or the water collected in greywater filtration systems – remains prohibited by households to use in most capacities and cannot be used in the same way as greywater. 

While extremely limited and experimental authorisations apply, they are typically made at an individual level by the departmental prefect.

New rules for usage to combat drought risks

Previously, the use of greywater was heavily restricted in France as it can contain chemicals and materials from cleaning products such as laundry detergent and soap, for example. Similar to blackwater, individual authorisation was required by the prefecture.

These limits were based on a 2015 report from the French food, work, and health agency Anses (Agence nationale de sécurité sanitaire de l'alimentation, de l'environnement et du travail). 

In a bid to reduce water waste – and following further studies by Anses – the government updated regulations in 2024. An overview of the regulations can be found here.

Greywater (eaux grises, not eaux grises issues des cuisines from the kitchen) can now be used for: 

• Washing laundry (in a washing machine or by hand)

• Cleaning indoor flooring

• Watering vegetable gardens or ornamental green spaces outside such as lawns or plants

• Use in decorative fountains not intended for drinking purposes

• Flushing toilets

• Cleaning certain outdoor surfaces

• Washing vehicles

Using greywater for laundry, indoor floor cleaning and vegetable garden watering are part of ‘experimental’ rules and are only authorised until 2034. They may be included as permanent uses based on studies and reviews.

You can therefore use any collected greywater in parts of your garden, provided the vegetables or foods you are growing are not sold and are only used for personal consumption (use of greywater for agricultural and commercial purposes fall under separate rules than those for residential homes). 

You must ensure that you minimise the risk of greywater entering the drinking water (eau potable) system. 

Similar rules also require you to limit the runoff from water used outside when cleaning vehicles to ensure it does not enter into the water network. 

Installation of filtration system required 

If you plan to collect greywater from your shower, bath, washing machine, or bathroom sink, you will need to set up a full filtration system. This water cannot be collected without being filtered.

You must ensure that there is a complete separation between the eau potable and eaux grises networks, mechanisms to prevent backflow leading to contamination, and ensure the water runs through separate pipes that are clearly marked. 

You must inform the local prefect of your planned installation, which can be done online through this official link.

Note that if you are planning to use the water for one of the ‘experimental’ purposes above – including watering plants – you still require authorisation from the prefecture as opposed to merely informing them of your plans.

This is also the case for kitchen wastewater. 

It is banned from use for ‘experimental’ purposes, and for all other uses you must obtain permission from the local prefecture.

Installing a filtration system linked to the kitchen sink will be more expensive than the traditional greywater sections, and will also limit you from using the waste water for all the ‘experimental purposes’ above, unless it has its own entirely separate filtration system.

Installations must adhere to rules set out in article R.1322-98 of France’s public health code.

Note that people living in shared flats may be limited from collecting such greywater in any capacity, and should check copropriété regulations before planning to install such a system. 

Water collected from your shower, bath, etc, can only be used to water ornamental lawns (provided there is no risk of runoff into the public network) as well as soil around the plants, and does not come into contact with any edible surfaces.

To minimise the risk of any health issues, consider using biodegradable laundry detergent, soap, etc.

However, you can also use leftover water collected from cleaning fruits and vegetables, or boiling foods, which will not have been contaminated with detergents or soaps, as long as you do not throw the water down the kitchen sink. Such water is not classified as waste water in any way, so can be used freely.

This water has the advantage of not needing to be filtered before being used in the garden, and is allowed to come into contact with the edible parts of plants, fruits, etc. 

Collected greywater should be treated within 12 hours of being collected, and used within 72 hours of being treated, however Anses recommends using it within 24 hours.