Urban Planning, Ecological Transition, Urban Services and Housing

The new by-law on greywater is aimed at the reuse of water from baths and showers in housing. The process starts with a participatory process and the hope is for it to be approved at the end of this year.

Greywater refers to the domestic water we use when we have a bath or a shower at home. Using a suitable collection and treatment system, this water can be put to other uses, for instance cisterns. The saving achieved could potentially reach 30% of safe water.

With this as the goal, the first steps are now being taken towards the new by-law on greywater for new buildings and major renovations. The first step will be a participatory process with users, public stakeholders and technicians, organisations and the general public.

Estimates put the volume of grey water generated by a household of four people at 200 litres a day, with each person using an average of 35 litres a day flushing the toilet. The investment required to install the reuse system is minimal and is quickly recovered, allowing for a direct saving of 90 euros a year per home in a block of 16 homes and up to 170 euros a year per home in a block of 50 homes, on top of the direct environmental benefits from cutting the consumption of safe water.

The new by-law on greywater in the city of Barcelona is part of the plan for alternative water resources in Barcelona (PLARHAB) and the climate emergency action plan 2030.

Boost for the groundwater network

The future by-law comes in addition to the enlargement of the groundwater network, that is, the water extracted from below ground. This water is not fit for human consumption, but can be used for tasks such as street cleaning. Work on the network will boost the volume of available groundwater by up to 20%.

The measures include the following:

• New tank for the area around the Jardins de Joan Brossa: this will provide another 50,000 cubic metres for the Montjuïc system.
• Up to 10,000 additional cubic metres per year for watering and the springs around the Zona Franca, distributed using pipes connecting with the future tank at Can Batlló.
• New tank in the Parc de Joan Miró, connection between the Parc de les Glòries and C/ Consell de Cent to gain 20,000 cubic metres.
• New well and improvements to the distribution pipes for the Taulat system: 50,000 additional cubic metres.
• New distribution pipe network to cross Av. Diagonal, at Palau Reial, to supply the side of the avenue nearest the mountains: 15,000 additional cubic metres.