As rainwater passes through the atmosphere, runs off roofs, into storage tanks and then into the supply network, it can become laden with metals, organic matter, organic micropollutants and micro-organisms.
A Ministerial Order of 21 August 2008 on the recovery of rainwater and its use inside and outside buildings specifies the conditions for using rainwater recovered downstream of inaccessible roofs, in buildings and their outbuildings, as well as the conditions for installing, maintaining and monitoring the equipment needed for its recovery and use. This Order authorises the use of rainwater outside homes (domestic uses and watering of green spaces) and indoors (for flushing toilets and washing indoor floors). The use of rainwater for washing laundry is authorised on an experimental basis, subject to the implementation of suitable water treatment systems.
The Directorate General of Health made a formal request to ANSES to "define the potential health risks, both direct and indirect, that could be posed by the implementation of a system for the recovery and use of rainwater, connected to a washing-machine, and assess the water treatment procedures that may be necessary to enable rainwater to be authorised for washing laundry."
Agency conclusions and recommendations
Given local variations depending on the season, the rainfall (duration of the rainfall event, dry-weather periods, etc.), the temperature, the characteristics of the system, the geographical location (rural/urban), the nature and characteristics of the catchment area and the surfaces over which the rainwater flows, the Agency concludes that it is impossible to identify and fully characterise the dominant microbiological and chemical hazards in a rainwater recovery system connected to a washing machine. Moreover, the situation relating to the recovery and use of rainwater in France in general, and for washing laundry in particular, is not well documented, despite Article 5 of the Ministerial Order of 21 August 2008 requiring its use to be notified to municipal authorities.
This expert assessment concludes a cycle of work by the Agency on the various technological measures and developments implemented to address the health issues associated with occasional and/or sustained risks of water shortages.
Given the heterogeneity of the available data, local conditions and individuals' laundry washing practices, and the fact that a risk assessment could not be conducted, it is impossible to propose quality limits for the water supplying washing machines, or for the generic treatment of rainwater for machine-washing laundry.
In addition, a washing machine is not a sterile environment and contains microbial populations consisting of micro-organisms from the water supply, biofilms and/or the dirty laundry. These various micro-organisms may be found on the laundry when it is taken out of the washing machine. Their fate on the laundry is closely linked to the washing conditions (temperature, detergent products, cycle, and quality of the rinse water), to the other steps in the laundering process (drying, ironing), and to their combined effect. The Agency therefore advises against using rainwater for laundering items for the following populations :
- people at risk of skin allergies, with skin diseases or atopic (allergy-prone) skin;
- young children, who regularly put laundry into their mouths;
- immunocompromised people;
- people receiving hospital care at home;
- hospitalised patients whose laundry is washed at home, and their families;
- people living next to industrial and agricultural sites, where the rainwater is likely to contain more chemical contaminants.
ANSES advocates drafting a good practice guide on laundry washing, regardless of the type of water used, to help inform people about the laundry care practices (sorting laundry, temperature, ironing) to be implemented in order to optimise laundry hygiene.
ANSES wishes to emphasise that health issues and risks exist with regard to the use of non-potable water for domestic purposes inside the home, involving the indoor construction of a non-potable water system. The Agency therefore reiterates its recommendations aiming to avoid the risk of confusion and interconnection of systems for the public water supply and for non-potable water inside buildings. For this, it is important to put in place a means of clearly identifying the systems (colour, pictograms, etc.), which can be understood by all users, including the visually impaired, those unable to read and those not fluent in French. It is therefore essential to ensure compliance with the technical requirements of the Order of 21/08/2008, the NF 16-005 Standard (rainwater) and the NF EN 1717 Standard (Protection of the water supply intended for human consumption), and in particular with the requirements concerning the disconnection of water circuits, maintenance, and drain valves inside buildings.
Lastly, ANSES recommends that investigations into the presence of a non-potable water system should be made before the sale of any house.