from the sanitary tee to the 90° ell will run parallel to the outside wall of the house. Measure and record distance X. Insert a length of 1½″ pipe through the opening in the sole plate for the drain from the kitchen sink. Check this pipe for plumb and measure the distance from the centerline of this pipe to the inside of the header (Y). See Measurements insert. Subtract Y from X to obtain the horizontal distance (Z) between the two centerlines. height of the 2″ sanitary tee depends on the posi- tion of the 1½″ 90° ell leading to the kitchen sink. The ell must be low enough for the horizontal pipe to run below the floor joists. In addition, the horizontal pipe must be installed with a fall of ¼″ per foot of run. The following steps describe the procedure for completing this installation. Place a length of 2″ pipe in the test tee so it extends upward between the floor joists. This pipe will be used as a reference for measurement, so it will need to be plumb. The horizontal pipe Fall @ 1⁄4″ per foot of run: 31⁄2′ × 1⁄4″ per ft. = 7⁄8″ total fall 143⁄4″ Mark centerline of 90° ell Mark here A 23⁄8″ B X Y Z TP Laying length Laying length P 3′-6″ Floor joist Studs Sole plate Subfloor Blocking 45° ell 90° ell Side View 90° ell 45° ell Sole plate Header Sill Foundation 2″ pipe 11⁄2″ pipe Measurements Theoretical Length Actual Length TP 90° ell 45° ell Calculating Fall Goodheart-Willcox Publisher Figure 19-9. Locating drain for kitchen sink. 304 Section 3 Plumbing System Design and Installation Copyright Goodheart-Willcox Co., Inc.