The most frequent and well-known problems are:
limestone encrustations,
corrosions
bacterial regrowth (for example the well-known phenomenon of Legionella Pneumophila).
Incrustations have the strongest influence on the thermal efficiency of the systems. In fact, upon heating, the bicarbonates and carbonates of calcium and magnesium in water generate calcium carbonates and magnesium hydrates, i.e. insoluble salts that deposit on the heat exchange surfaces and reduce the energy efficiency of the plants.
1 mm of limestone incrustation corresponds to 50 mm of steel as a heat exchange capacity. And again, 1 mm of limestone is able to reduce the heat exchange capacity of a generator for the production of domestic hot water by 18% or more.
With regards to the primary circuit, very recent studies have highlighted how the absence of proper water treatment, with the appropriate conditioning products, reduces the energy efficiency of the system by 6% in just 3 weeks. The sum of these problems can lead to energy waste of € 400 per family. All this without considering other negative side effects such as the consequent increase in CO2 emissions in the environment, the reduction of the useful life of all appliances, the reduction of the hygienic conditions of the systems (Legionella lurks much more easily in limestone deposits) and a drastic reduction in operational safety levels.