Section 890.410  Fixture Traps/Continuous Waste


a)         Fixture Traps.  All directly connected plumbing fixtures, except those having integral traps, shall be separately trapped by a water-seal trap, placed as close to the fixture outlet as possible.  A kitchen sink with up to three basins may be installed on one trap if one compartment is not more than 6 inches deeper than the other and the waste outlets are not more than 30 inches apart.  (See Appendix D.Illustration A.)


b)         Distance of Trap to Fixture.  The developed length from the fixture outlet to the trap weir shall not exceed 24 inches, except that an interceptor used as a trap shall be located as close as possible to the fixture.  The maximum developed length from the fixture outlet to the inlet of the interceptor shall not exceed 5 feet.  (See Appendix D.Illustration B.)  The standpipe inlet for an automatic clothes washer shall not exceed 48 inches above the weir of a trap.


c)         Trap Size.  The size of trap for a fixture shall comply with Appendix A.Table E for minimum size of traps.  No trap shall be larger than the fixture drain to which it is connected or the drainage pipe into which it discharges.


d)         Type of Traps.  Traps shall have a uniform and smooth interior, and shall have no partitions or movable parts.  The trap seal shall be non-adjustable.  (See Appendix D.Illustration C.)


e)         Drum Traps.  Drum traps shall be 3 or 4 inches in diameter and provided with a fixed water seal of at least 2 inches.  The trap cleanout shall be one size less than the trap diameter.


f)         Trap Seal.  Each trap shall have a water seal of 2 inches except where a deeper seal is required to prevent the loss of the trap seal by evaporation.  Where loss of the trap seal may occur due to evaporation, one of the following shall be used:


1)         Vegetable oil may be added to the trap.


2)         A deeper seal not to exceed 8 inches may be used.


3)         An automatic trap primer may be used.


g)         Trap Cleanouts


1)         Each fixture trap, except those cast integrally or in combination with fixtures in which the trap seal is readily accessible or except when a portion of the trap is readily removable for cleaning purposes, shall have an accessible threaded or cam lock cleanout plug of ample size protected by the water seal.  (Exception:  See subsection (g)(4).) The cleanout plug shall be of brass or other non-corrosive type material.  (See Appendix D.Illustration D.)


2)         Trap cleanouts shall be made gas and water-tight with a threaded cleanout plug and approved washer.


3)         A P-trap that is used on a bath waste shall be directly below the tub overflow.  The overflow shall be fastened to the tub by means other than the face plate.


4)         A P-trap on a plumbing fixture that is not accessible may be installed without a cleanout plug or having a portion of the trap readily removable, provided that there is access to a cleanout within 3 feet of the trap.


h)         Trap Level and Protection.  Traps shall be set level with respect to their water seals and, where necessary, they shall be protected from freezing.


i)          Traps Underground.  Underground traps shall be provided with accessible and removable cleanouts, except for separate "P" traps into which floor drains, urinals and other fixtures with removable drain strainers discharge.


j)          Building (House) Traps.  No trap shall be installed at the base of a soil or waste stack or in a building drain.


k)         Prohibited Traps.  Use of the following traps is prohibited (see Appendix D.Illustration E):


1)         Traps that depend upon the action of movable parts for their seal;


2)         Full "S" traps.  Exception:  Water closet and similar fixtures that depend on self-siphonage for their proper operation;


3)         Bell traps;


4)         Crown vented traps;


5)         Unvented running traps; and


6)         Fixtures with concealed interior partitioned traps.  Exception: Fixtures with integral traps constructed of vitrified earthenware and penal institutional fixtures with integral traps constructed of ferrous material.


l)          Double Trapping.  No fixture shall be double trapped.


(Source:  Amended at 38 Ill. Reg. 9940, effective April 24, 2014)