The government of Mayor Jaume Collboni is already preparing a new municipal ordinance aimed at the use of what is known as gray water. The objective of Barcelona City Council is that the homes in newly built buildings, as well as those undergoing major renovations, have the appropriate infrastructure so that their toilet cisterns are supplied with the water that is normally lost through shower and bathtub drains. The water that is diluted in bidets, sinks, sinks, dishwashers and washing machines is too dirty.
Municipal sources detail that the processing of the new ordinance now begins with the corresponding citizen participation process, that the objective of the municipal executive is for the new regulations to come into force at the end of the year, at the beginning of 2025 at the latest. The accounts and calculations of the technicians reveal the reasons for this haste.
A household of four people generates around 200 liters of gray water every day. Each person spends an average of 35 liters flushing the cistern. Showers and bathtubs account for the majority of domestic drinking water consumption. And the tankers occupy second position. Reuse systems reduce domestic drinking water consumption by more or less 30%. We are talking about a potential annual saving in Barcelona of around 300,000 m3. This is an estimate based on the urban development of the city over the last five years.
Meanwhile, works aimed at making even more use of groundwater in the subsoil continue at a good pace. This municipal investment is around 14.4 million euros. Barcelona City Council trusts that these improvements will be ready next year. Who knows what emergency phase of the drought we are in then.
In reality, many people have always used basins to take advantage of the water that was lost through the drains in their bidets, showers, bathtubs, washbasins and sinks to the extent possible, especially in places where drought was always more than just a circumstantial situation.
The first municipal ordinance of this type is that of Sant Cugat del Vallès, in operation since 2002. Experts also highlight the ordinance for the efficient management and use of water in Madrid from 2006. In addition, after 2010, other texts follow one another in municipalities of Andalusia, Galicia and Murcia. The Spanish Association of Water Treatment and Control Companies already published in 2011 a technical guide on the use of gray water for administrations, professionals, users…
The new Barcelona ordinance is part of the Alternative Water Resources Plan of the city of and the action plan for the climate emergency 2030, whose main objective is to turn the Catalan capital into a city more prepared against climate crises. The regulations in process will affect all newly built buildings and large renovations of more than 16 homes or that have a consumption of more than 500 m3 per year in showers and bathtubs.
Previous analyzes indicate that in these cases the investment in this system is profitable. These properties will only have to incorporate a small treatment plant where gray water will be treated so that it can be reused again in toilet cisterns. Families will be able to save about 100 euros a year in this way.
These obligations have been in operation for a couple of years in the district of Gràcia and 22@ by virtue of a modification of the General Metropolitan Plan. Furthermore, the municipal public development of 54 homes in the Besòs neighborhood where the City Council presented this initiative also takes advantage of its gray water. Two other municipal developments still in construction will also do so.
The biggest drawback of this system is that if you spend a few days away from home without flushing the toilet, you may find yourself with a bad smell when you return. But the technical guide on the use of gray water says that it is enough to add a disinfectant tablet to the cistern before leaving on vacation and give it four times when you return.
