Providing enough water to stock is essential for high milk production. Clean water is also required in large quantities for cooling milk and washing the milking plant. Some key principles, measurements and water requirements are noted here. Accompanying Farmfact 5-18 provides tips for efficient water use in the farm dairy. Farmfact 5-19 addresses management of stock drinking water, while irrigation is covered in Farmfacts 5-20 to 5-23.