This is a bonus provided and governed by ARERA (the Authority for the Regulation of Energy, Networks and Environment), through deliberation 227/2018/R/ IDR.
From 1 January 2021, individuals/families in financial difficulty and entitled to social benefits and bonuses will receive them automatically without having to apply. Anyone entitled will no longer be required to apply through their Municipal Authority or Tax Assistance Center (CAF). Starting in 2021, the only thing individuals/families will have to do every year is submit their Single Self-Declaration (DSU) to obtain the ISEE certificate required to have access to welfare benefits. All details can be found on the water bonus page of the ARERA website.