Using graywater for hand washing is a strategy for reducing indoor water use, as it can save potable water that would otherwise be used for this purpose. Graywater is the wastewater that is generated from activities such as bathing, laundry, and dishwashing, which can be treated and reused for non-potable applications, such as toilet flushing, irrigation, and hand washing. Using graywater for hand washing can reduce the indoor water use by up to 40%, according to a study by the Pacific Institute1. LEED v4 recognizes and rewards this strategy in the Indoor Water Use Reduction credit2, which aims to reduce the potable water consumption of a building by at least 25% compared to a baseline3. The other options are not directly related to reducing indoor water use, as they involve different types of measures or systems that are not relevant for saving potable water.