Among the unique buildings of the town hall, we must highlight the one that houses the Emalcsa water treatment plant in Cañás, on the banks of the Barcés River. This Modernist-style building was built in 1908 and extended in 1922. It was built to supply the city of A Coruña, and did so until 1940, when the high demand for drinking water levels exceeded the capacity of this treatment plant. The Telva plant in Cambre was then built to meet the needs of the city. Now the Cañás plant purifies the water from the Barcés River to supply only Carral.
This treatment plant was once avant-garde, as it had rapid filters made of wood according to the German Reisert system. It was the second treatment plant in Spain to supply filtered water to the population.