Copyright Goodheart-Willcox Co., Inc. 313 OBJECTIVES After studying this chapter, you will be able to: ■ ■■ Use a schematic DWV drawing to size DWV piping. ■■ Compare and use the three methods of measuring pipe length between fittings. ■■ Describe proper procedures for locating and installing DWV piping systems. ■ Use the prescribed techniques for working with plastic, copper, galvanized iron, black iron, and cast-iron DWV materials. TECHNICAL TERMS center-to-center drainage fixture unit (d.f.u.) face-to-face flashing laying length shoulder-to-shoulder Isecond n the first rough stage, the building sewer and water supply are installed. These pipes extend from the water and sewer mains to the inside of the building. The rough stage is the installation of all plumbing that will be enclosed in the walls or that must be installed before the walls are finished. This includes DWV, hot and cold water supply piping, bathtubs, and shower bases. The second rough stage of DWV installation is critical because the correct size of pipe must be installed and required slope must be maintained in horizontal runs of pipe. Also, pipes and fittings must be placed accurately so fixtures can be hooked up easily during the finish stage. Procedures for completing layout and making modifications to the structure were discussed in Chapter 20. This chapter focuses on the actual installation of DWV piping systems. In the following section, sizing of pipe, and techniques for measuring pipe are discussed. This will give you back- ground for the section that provides an overview of the DWV installation. Later sections of this chapter describe procedures for installing the various types of pipe and fittings typically used for DWV systems. 21.1 Sizing DWV Piping The schematic drawing in Figure 21-1 provides the data used to determine the size of each part of DWV piping for a one-story single-family home with a basement. The first step in the process is to quantify the load that fixtures place on the DWV piping. Load is given in drainage fixture units (d.f.u.). IRC Chapter 30, Section P3004, provides a table giving the d.f.u. for plumbing fixtures. In Figure 21-1, the d.f.u. values for individual fixtures and groups of fixtures are printed in red. Note that the d.f.u. for a group of fixtures is less than the total of the d.f.u. for all of the individual fixtures in the group. This is because it is unlikely that all of the fixtures in the group will be used at the same time. C H A P T ER 21 DWV Pipe and Fitting Installation