the fitting. Add the appropriate fitting allowance and cut the pipe to join the test tee with the double sanitary tee w/side inlet. In our example, two short lengths of 3″ pipe and a 90° sanitary ell are used to connect the closet flange to the double sanitary tee. The horizontal pipe from the double sanitary tee must have a fall of ¼″ per foot of run. The length of the horizontal pipe can be determined by temporarily inserting a 3″ pipe in the closet flange and measuring (A) from the centerline of the pipe to the 3″ inlet at the double sanitary tee, Figure 19-21. The laying length (3″) of the 90° ell must be subtracted from measure- ment A and the fitting allowance (1½″) for the double sanitary tee must be added to determine the length (B) of the pipe (16″ – 3″ + 1½″ = 14½″). Once the horizontal pipe is cut, temporarily assemble the pipe in the double sanitary tee and slip the 90° ell into place. Check the fall of the horizontal pipe and measure the distance between the 90° ell and the closet flange. Add ing the fitting allowances to this measurement gives the length of the vertical pipe. The closet flange will not be permanently secured until after the finish floor is installed. Test tee w/ cleanout Mark here and add fitting allowance to determine length of pipe connecting test tee and double sanitary tee. 1″ 23⁄8″ fall 33⁄8″ Floor joist Studs Sole plate Subfloor 3″ pipe fitted in test tee @ base of stack Alternate: If the P-trap will extend too far below the floor joist, the end of the run can be turned up between the floor joists. Goodheart-Willcox Publisher Figure 19-20. Location of the double sanitary tee depends upon the fall required for the bathtub. L = Laying length L Level to check plumb Shims equal in thickness to finished floor 3″ pipe Floor joist Stud Sole plate Closet flange Double sanitary tee 3″ pipe B A A Goodheart-Willcox Publisher Figure 19-21. Joining the closet flange to the double sanitary tee requires two short lengths of pipe and a sanitary ell. Chapter 19 DWV Pipe and Fitting Installation 311 Copyright Goodheart-Willcox Co., Inc.