a combination of a wye and a 22½° or 45° elbow will be needed. Once the location of the hori- zontal pipe is determined, a trench can be dug to permit its installation. Trenches must be sloped so they provide a fall of ¼″ per foot of run. Generally, the top of the concrete floor for a basement will be 4″ above the top of the footings. This dimension should be checked so the depth of the trench can be determined. A short trench will also be needed for the floor drain. The size of pipe and fittings in a DWV system is computed based on drainage fixture units as specified in the code. of the fittings at the base of the stack, Figure 19-4. If necessary, excavate in order to position the long-radius ell at the correct elevation. It may be necessary to break away some of the footing so that the long-radius 90° ell will fit close to the foundation wall. To locate the horizontal waste pipe, stretch a string line from the base of the bathroom stack to the building drain. A shallow trench will need to be dug along this line so that the waste pipe can be installed. A second string line can be run from the base of the kitchen/laundry stack to the point where it will join with the first horizontal waste line. (Refer to Figure 19-3.) This joint must be made with standard fittings, so the intersection should be at an angle of 45° to allow a standard wye to be used. In cases where this is not possible, Minimizing Waste of Pipe and Fittings Plumbers can do several things to minimize waste of pipe and fittings. First, and possibly most important, is for the plumber to understand what the job requires and plan the installation to avoid the use of excess pipe and fittings. Saving even a few feet of pipe or several fittings on every job becomes a very large savings during the career of a plumber. The following practices help minimize waste: • Storing and handling pipe and fittings so they are protected from damage and can be located easily. This practice contributes to efficiency and encourages the use of short lengths of pipe. • Checking measurements and calculations before cutting pipe to minimize errors, thus reducing waste. • Using as much of each length of pipe as practical. • Selecting the most appropriate fitting rather than combining two or more fittings. Using a reducing tee rather than a standard tee and a reducer is an example of this practice. • Recycling any unusable or damaged fittings and short lengths of pipe. Can you think of other things you could do to minimize amount of pipe and fittings that are wasted? Block Closet bend Sanitary tee Plumb bob Y Finish floor line 1⁄8 bend Concrete Cleanout Goodheart-Willcox Publisher Figure 19-4. To locate the fitting at the base of the stack, suspend a plumb bob through the center of the sanitary tee. Concrete can be placed later to provide solid support for the weight of the stack. 300 Section 3 Plumbing System Design and Installation Copyright Goodheart-Willcox Co., Inc.