Recent national government policy in Ireland proposes a radical transformation of the energy sector and a large reduction in CO2 emissions by 2050. Water and energy form the water−energy nexus, with water being an essential component in energy production. However, the connection between the production of energy and water is rarely made. In particular, the end-user processes are generally excluded because they occur outside the water industry. The present study includes two simple approaches for industrial sites to calculate their carbon footprint in the water sector. The assessment of the milk powder manufacturing using both approaches indicates that the combined emission factor of the water supply and treatment is approximately 1.28 kg CO2 m−3 of water. The dairy production among steel, textile, and paper industries appears to be the most carbon-emitting industry. However, the results show that the carbon intensity of the water supply and treatment can be minimized by the integration of renewable energy sources for the onsite heat/steam and electricity generation. The uniqueness of our approaches compared to calculations illustrated by the ecoinvent and other governmental databases is its simplicity and a focus on the main energy consuming manufacturing steps in the entire industrial process. We believe that the management of water and energy resources will be more efficient when “active water citizens” raise environmental awareness through promoting measures regarding data monitoring and collection, observed leaks and damages, dissimilation and exchange of information on sustainable water stewardship to public and various industrial stakeholders.