Why Water Demand Calculation is crucial First Step in Plumbing System Design.

Calculating water demand is a critical first step in MEP system design. It ensures that plumbing networks, storage reservoirs, and municipal connections are accurately sized to meet user needs while preventing wastage. Beyond this, water demand assessment forms the basis for sizing sewage treatment plants (STPs) and estimating the volume of treated water available for reuse, thereby enhancing overall water efficiency. In India, the National Building Code (NBC) 2016 Part 9, Plumbing Services provides comprehensive guidelines for determining water requirements across different building types. Key Factors Considered in Water Demand 1. Residential, commercial, institutional, industrial, or mixed-use each have different per capita water requirements. 2. Special Provisions like Firefighting demand, landscaping, irrigation, HVAC makeup water and other non-potable uses. NBC 2016, Chapter 9 has clearly laid out the inclusions and exclusions in water requirement for various types of project. For eg. For a residential building the water demand is 135 lphd, which is inclusive of domestic and non-domestic needs. Meanwhile Hotel projects it is 180 to 320 per head water demand and are exclusive of Kitchen, Laundry, Staff and other requirements. These requirements need to be incorporated separately. Lastly, the quantity of discharge water, which is crucial to determine the size of STP, is also determined at design level by the water demand calculations. The amount of water to repurposed for domestic needs, along with the water required for irrigation can be determined henceforth. By adhering to NBC 2016 guidelines, designers and MEP professionals ensure: • Adequate supply to all occupants. • Optimized plumbing system design. • Regulatory compliance and smooth project approvals. • Sustainable water uses by avoiding over design. Water is a precious resource, and its demand must be carefully estimated in every building project. The NBC 2016 norms provide a standardized framework that balances user comfort, system efficiency, and long-term sustainability. Whether it’s a home, hospital or hotel, following these guidelines ensures that water infrastructure is both reliable and responsible.