Section 890.1350  Offsets in Drainage Piping

a)         Offsets of 45 Degrees or Less.  An offset in a vertical soil or waste stack with a change of direction of 45 degrees or less from the vertical shall be sized as a straight vertical stack.  If a horizontal soil or waste branch connects to the soil or waste stack within two (2) feet above or below the offset, a relief vent shall be installed in accordance with Section 890.1550(c).  (See Appendix J:  Illustration G.)

b)         Offsets of More Than 45 Degrees.  A soil or waste stack with an offset of more than 45 degrees from the vertical shall be sized and installed as follows:

1)         The portion of the stack above the offset shall be sized as for a regular stack based on the total number of drainage fixture units above the offset.

2)         The offset shall be sized as for a building drain.  (See Appendix A:  Table G.)

3)         The portion of the stack below the offset shall be sized as for the offset or based on the total number of drainage fixture units on the entire stack, whichever is larger.  (See Appendix A:  Table L.)

4)         The drain offset shall have a relief vent installed as provided in Section 890.1550.  In no case shall a horizontal soil or waste branch connect to the soil or waste stack within two (2) feet above or below the drain offset.  (See Appendix J:  Illustration H.)

c)         Above Highest Branch.  An offset above the highest horizontal waste branch is an offset in the stack vent and shall be considered only as it affects the developed length of the vent.  (See Appendix J: Illustration I.)

d)         Below Lowest Branch.  In the case of an offset in a soil or waste stack below the lowest horizontal branch, no change in diameter of the stack shall be required because of the offset if it is made at an angle of not greater than 45 degrees.  If such an offset is made at an angle greater than 45 degrees, the required diameter of the offset and the stack below it shall be determined as for a building drain.  (See Appendix A:  Table G, and Appendix J:  Illustration J.)