What is the first step in the procedure for sizing domestic water systems?

The first step in the procedure for sizing domestic water systems is to draw a riser diagram of the water distribution system. This diagram serves as a visual representation of the overall layout and configuration of the plumbing system, which includes the location of fixtures, the types of pipes needed, and how they connect to the water source. By creating a riser diagram, designers gain a better understanding of the system's flow paths, which is essential for accurately assessing pressure losses, flow rates, and the selection of appropriate pipe sizes.

Having this visual aid allows for better planning and helps identify potential issues that could arise during installation or operation. It sets a solid foundation for the subsequent steps, such as converting fixture units (FU) to gallons per minute (GPM), determining pressure requirements, and selecting pipe sizes, as these calculations and decisions are inherently dependent on the accurate representation provided by the riser diagram.