As the global push towards achieving Net Zero intensifies, the significance of green hydrogen as a clean energy carrier has come to the forefront. Central to the production of green hydrogen through electrolysis is the requirement for water both as a feedstock and for system cooling. While theoretically 1kg of hydrogen can be produced with around nine litres of water, practical applications demand higher quantities due to the need for treated water meeting electrolyser standards, such as deionised water. Ensuring the water used in electrolysis meets specific quality standards like ASTM Grade II or equivalent is crucial to prevent damage to the electrolyser components and to maintain their operational lifetime as recommended by manufacturers. Additionally, water is essential for system cooling, albeit at a lower quality requirement. The article emphasizes the necessity of utilizing renewable electricity and water in the electrolysis process to facilitate the green hydrogen transition and advance a sustainable energy economy. The management and treatment of water in electrolysis operations play a pivotal role in enhancing the efficiency and dependability of green hydrogen production, underlining the interconnectedness of water resources and the hydrogen sector's growth.