distance from the centerline of the pipe to the floor joist must be added to the fall to determine the vertical distance of the side inlet of the double sanitary tee below the floor joists (2⅜″ + 1″ = 3⅜″). Hold the double sanitary tee in position so the center of the side inlet is 3⅜″ below the bottom of the floor joist and mark the pipe at the bottom of With the tubs/shower bases in position, it is time to locate the closet flanges for water closet installation in the correct openings. Support the closet flange on blocking equal in thickness to the finished floor material, Figure 19-18. Check the distance from the wall to the center of the closet flange. Temporarily secure the closet flange with a weight. Assemble the long-radius ell and cleanout at the base of the stack so the ell can connect to the horizontal sewer pipe. The height of the double sanitary tee w/side inlet that serves the two water closets is critical to this installation because of the need for ¼″ of fall per foot of pipe run to each of the P-trap inlets for the bathtubs. Given that the pipe going to each of the bathtubs is relatively long, the fall necessary for these pipes will be the determining factor in locating the double sanitary tee. Drawing lines on the subfloor to represent these pipe runs is an accurate means of determining the total run to each bathtub P-trap, Figure 19-19. Once the total run is known (9½′), the total fall is calculated by multiplying by ¼″ per foot of run (¼″ × 9½′ = 2⅜″). See Figure 19-20. The 1″ vertical Strainer Molded shower base Floor level To sewer 2″ waste pipe Strainer Lead Molded shower base Floor level To sewer 2″ waste pipe Oakum Compression gasket A B Goodheart-Willcox Publisher Figure 19-17. The connection between the shower drain and DWV piping must be sealed. A—Today, a compression gasket is typically used. B—Some older installation may be joined with lead and oakum. Check accuracy Blocking equal in thickness to the finish floor Closet flange Closet bend Double sanitary tee goes here Opening for stack Goodheart-Willcox Publisher Figure 19-18. The closet flange must be temporarily supported on blocks equal to the thickness of the fin- ished floor before measurements are made for the pipe connecting it to the stack. A 18″ B 24″ C 72″ Total run = A + B + C = 18″ + 24″ + 72″ = 114″ = 9½′ Total fall = Total run(′) × ¼″ per ft. = 9½′ × ¼″ per ft. = 9⁄4 = 1⁄8 = 23⁄8 Goodheart-Willcox Publisher Figure 19-19. The total run of the drain pipe to the bath- tub can be determined by a simple layout on the subfloor. 310 Section 3 Plumbing System Design and Installation Copyright Goodheart-Willcox Co., Inc.