A plant comprising a water filtering device with a motor pump, the device for chemically treating the water, the pipes with the corresponding valves and with the openings for receiving the water from the swimming pool and for returning the cleaned and treated water to the swimming pool, and the corresponding accessories are all connected and installed on a base framework allowing to transport the whole ready-to-operate plant to a chosen site. All of the components making up this plant can be distributed in independent modules being apt to be fitted to each other. The assembly being made up of all of the components and accessories of the plant, both if they are installed on a single base framework as well as if they are distributed in modules, is of such dimensions as to be apt to be put in a conventional container facilitating its transportation.