The NIRON PPR random copolymer polypropylene pipe and fitting system was installed for the open loop geo-exchange system with direct use of groundwater at the Vertical Forest residential buildings in Milan. The plant draws water directly from suction wells that draw from the surface aquifer, i.e. the first aquifer present in the subsoil. The water is sent to the heat pumps, where the heat exchange takes place and then returns to the source. The distance between the suction and re-entry wells must be such as not to interfere on the piezometric of the underground aquifer. A high concentration of ferrobacteria, aerobic microorganisms that obtain carbon from carbon dioxide and derive energy for their livelihood from the oxidation of iron has been found in the area. These bacteria accelerate the reaction that occurs naturally between oxygen and ferrous ions present in the water, or on the surface of the metal pipes, and increase the presence of ferrous precipitate (ferric hydroxide) in the water. This causes the presence of a strong fouling of the metal pipes with occlusion of the filters and loss of system efficiency. All the pipes of the Vertical Forest building system were made of carbon steel, including the uprights for irrigation of the green terraces of the houses, which drew water from the aquifer itself. The latter, in the smaller sections, were completely blocked by the ferrous precipitate. The decision was then taken to replace the entire well water vectorisation system for the towers of the Vertical Forest buildings with a system with exceptional chemical inertia and oxidation resistance, i.e. the NIRON system by NUPI in PPR.