sanitary tee 2⅜″ below the floor joist and mark the 2″ pipe at the bottom of the fitting. Add the fitting allowance and cut the 2″ pipe to length. Temporarily install the 2″ pipe and the sani- tary tee. Measure distance B from the sanitary tee to the 90° ell and add the appropriate fitting allowances. Cut and test the fit of the pipe. The next step in installing the kitchen sink drain is to determine the length of the pipe from the 45° ell to the 90° ell at the stub-out. Since a length of pipe is already in position, the rough-in height (assume 14¾″ above the sub-floor: 14″ rough- in + ¾″ for the finished floor) can be marked directly on the pipe. Subtract the laying length of the 90° ell and cut the length of pipe. A short length of 1½″ pipe and a cap will be needed to complete the stub-out. The pipe should be long enough that the stub-out will extend 3″ through the finished wall material. This will permit the cap to be cut off and an adapter installed during the finish stage of plumbing installation. Given the number of pieces that have been temporarily joined, permanently assembling these components will help keep everything in position while the stack is completed. The horizontal 1½″ pipe will need to be secured to the floor frame near the 90° ell and the vertical pipe leading to the stub-out will need to be securely fastened to the blocking. The offset for the 2″ stack can be done the same way the offset for the sink drain was fabri- cated. The centerline of the 2″ pipe from the base- ment was previously determined to be 11″ from the inside of the header (X). Insert a length of 2″ pipe through the opening in the sole plate for the stack. Plumb this length of pipe and measure the distance from the centerline of the pipe to inside of the header (Y). With these two dimensions, repeat the process described in Figure 19-9 to calculate the length of pipe necessary to join the two 45° ells required to offset the stack at the top of the foundation wall. It is extremely important that the fittings be correctly positioned so their outlets will align with branch piping. To assure correct alignment, make a trial assembly of the pipe and fittings and mark the position of the pipes at joints as shown in Figure 19-10. Marking permits the fittings to be repositioned after the joints have been prepared. Also, it will be possible to lay the pipe on a flat work surface or secure it in a vise while joining subassemblies. The theoretical length (TP) of the short 45° angled 1½″ pipe that will connect the 90° ell and 45° ell can be determined by calculating the hypot- enuse of a right triangle with sides of length Z (see Chapter 4). An alternative is to know that the hypotenuse (TP) of a 45° right triangle is 1.41 times the length of a side. Therefore, if Z = 9½″ or 9.5″, TP = 9.5″ × 1.41 = 13.42″ (137⁄16″). See Theoretical Length insert. To find the actual length of the pipe required (P), the laying length of the two fittings must be subtracted from TP. See Actual Length insert. The laying length for the 90° ell in this example is 1¾″. The 45° ell has a laying length of 1⅛″. Therefore, T = 137⁄16″ – 1¾″ – 1⅛″ = 99⁄16″. Cut this length of pipe and temporarily join the 45° and 90° ell to the 99⁄16″ length of pipe and to the length of pipe extending down from the kitchen. Position the 90° ell so that the open end is facing the stack and is at the correct height to allow the horizontal pipe that will extend to the stack to be secured to the underside of the floor joists, Figure 19-10. Measure the distance A from the centerline of the 90° ell to the floor joist. For this example assume that A = 1½″. To calculate the height of the sanitary tee inlet, it is necessary to allow for a fall of ¼″ per foot of run. See Calculating Fall insert. This means the centerline of the inlet to the sanitary tee should be 2⅜″ (1½″ + ⅞ ″) below the floor joist. Hold the Mark with permanent marker Goodheart-Willcox Publisher Figure 19-10. Pipe and fittings are trial assembled. If satisfactory, position of fitting is marked as shown. Alignment is then certain to be correct when joints are made. Chapter 19 DWV Pipe and Fitting Installation 305 Copyright Goodheart-Willcox Co., Inc.