815 KAR 20:090. Soil, waste, and vent systems.


      RELATES TO: KRS 318.010, 318.015, 318.130, 318.150, 318.200, EO 2009-535

      STATUTORY AUTHORITY: KRS 318.130, EO 2009-535

      NECESSITY, FUNCTION, AND CONFORMITY: KRS 318.130 requires the office, after review by the State Plumbing Code Committee, to promulgate an administrative regulation establishing the Kentucky State Plumbing Code regulating plumbing, including the methods and materials that may be used in Kentucky for soil, waste, and vent systems. EO 2009-535, effective June 12, 2009, reorganized the Office of Housing, Buildings and Construction as the Department of Housing, Buildings and Construction, and established the commissioner, rather than executive director, as the head of the department. This administrative regulation identifies and publishes the manufacturer's specification number of the material accepted in the installation and design of soil, waste and vent systems in each type of plumbing system.


      Section 1. Grades and Supports of Horizontal Piping. (1) Horizontal piping shall run in practical alignment and at a uniform grade of not less than one-eighth (1/8) inch per foot, and shall be supported or anchored in accordance with the manufacturer's recommendations but shall not exceed ten (10) feet in length.

      (2) A stack shall be supported at its base and each pipe shall be rigidly secured.

      (3) No-hub pipe and fittings shall be supported at each joint of pipe and fittings.

      (4) Polyvinyl chloride and acrylonitrilebutadiene-styrene schedule forty (40) horizontal piping shall be supported at:

      (a) Intervals not to exceed four (4) feet;

      (b) At the base of each vertical stack; and

      (c) At each trap branch as close to the trap as possible.

      (5) Polyethylene pipe and fittings shall be continuously supported with a V channel.

      (6) A stack shall be rigidly supported at its base and at the floor level.


      Section 2. Change in Direction. (1) Except as provided in subsections (2), (3), or (4) of this section, a change in direction shall be made by the appropriate use of a forty-five (45) degree wye, half-wye (1/2), quarter (1/4), sixth (1/6), eighth (1/8) or sixteenth (1/16) bend.

      (2) A single sanitary tee may be used in a vertical stack.

      (3) A sanitary tee may be turned on its back or side at an angle of not more than forty-five (45) degrees.

      (4) A double sanitary tee may be used on a vertical soil, waste and vent line.


      Section 3. Prohibited Fittings. The following shall be prohibited:

      (1) A double hub bend and double hub tee or inverted hub on a sewer, soil or waste line;

      (2) The drilling and tapping of a house sewer or house drain, soil, waste or vent pipe;

      (3) The use of a saddle hub; and

      (4) Pipe installed with a hub or restriction that reduces the area or capacity of the pipe.


      Section 4. Dead Ends. In the installation of a drainage system, a dead end shall not be used.


      Section 5. Protection of Material. (1) A pipe passing under or through a wall shall be protected from breakage.

      (2) A pipe passing through or under cinder, concrete, or other corrosive material shall be protected against external corrosion.


      Section 6. Materials. (1) Main or branch soil, waste and vent pipes and fittings within or underneath a building shall be:

      (a) Hub and spigot extra heavy or service weight cast iron;

      (b) No-hub service weight cast iron;

      (c) Galvanized steel;

      (d) Galvanized wrought iron;

      (e) Lead;

      (f) Brass;

      (g) Types K, L, M, and DWV copper;

      (h) Standard high-frequency welded tubing produced and labeled with the latest ASTM specifications;

      (i) Types R-K, R-L, R-DWV brass tubing;

      (j) DWV brass tubing produced and labeled as ASTM B587;

      (k) Seamless stainless steel tubing;

      (l) Grade G or H produced and labeled as ASTM A-312;

      (m) Polyvinyl chloride schedule 40 or 80 produced and labeled as ASTM D2665, D1784, and F-891;

      (n) Coextruded composite PVC pipe produced and labeled ASTM F-1488;

      (o) Acrylonitrile-butadiene-styrene schedule 40 or 80 produced and labeled as ASTM D2661 or F-628; or

      (p) Silicon iron or borosilicate.

      (2) A main or branch soil waste and vent pipe and fittings underground shall either be:

      (a) Hub and spigot extra heavy or service weight cast iron;

      (b) No-hub service weight cast iron;

      (c) Type K or L copper pipe;

      (d) Type R-K, R-L brass tubing;

      (e) Lead; or

      (f) Silicon iron or borosilicate pipe and fittings or plastics DWV identified in this section.

      (3) Underground waste pipe installed beneath a concrete slab shall not be less than two (2) inches in diameter and shall extend no less than twelve (12) inches above the concrete slab.


      Section 7. Size of Soil and Waste Pipe per Fixture Unit on One Stack. (1) The following table, based on the rate of discharge from a lavatory as a unit, shall be employed to determine fixture equivalents:

Pipe Size

(In Inches)

Maximum Developed Length



1 1/4

25 ft.


1 1/2

60 ft.



80 ft.


2 1/2

100 ft.



225 ft.




















      (2) A water closet shall be on a minimum of a three (3) inch waste with a maximum of three (3) water closets or soil discharging fixtures per three (3) inch line.


      Section 8. Soil and Vent Stacks. (1) A building in which a plumbing fixture is installed shall have a soil or waste and vent stack, or stacks, extending full size through the roof.

      (2) A soil or waste and vent stack shall be as direct as possible and free from sharp bends or turns.

      (3) The required size of the soil or waste and vent stack shall be determined from the total fixture units connected to the stack in accordance with Section 7 of this administrative regulation except that more than three (3) water closets shall not discharge into a three (3) inch stack.


      Section 9. Future Openings. An existing opening or an opening installed in a plumbing system for future use shall be complete with its soil, waste and vent piping and shall comply with this administrative regulation.


      Section 10. House Drain. (1) The size of the house drain shall be determined by the total number of fixture units connecting to the house drain. The total area of vents through the roof shall be equal to that of the house drain with a minimum of one (1) three (3) inch stack.

      (2) If a three (3) inch house drain enters a building, it shall be attached to a three (3) inch stack. One (1) floor drain may be added to the house drain with a three (3) inch trap if it conforms with the requirements of Section 24 of this administrative regulation, without counting toward the fixture units of the system.


      Section 11. Soil and Waste Stacks, Fixture Connections.

      (1) A soil and waste stack or branch shall have correctly faced inlets for fixture connections.

      (2) Each fixture shall be independently connected to the soil or waste system.

      (3) A fixture connection to a water closet, floor-outlet pedestal sink, pedestal urinal, or other similar plumbing fixture shall be:

      (a) Cast iron;

      (b) Lead;

      (c) Brass;

      (d) Copper; or

      (e) Plastic closet bend.

      (4) A three (3) inch closet bend shall have a four (4) inch by three (3) inch flange.


      Section 12. Changing Soil and Vent Pipes in an Existing Building. In an existing building if the soil, waste and vent piping is not extended undiminished through the roof or if there is sheet metal soil or waste piping and the fixtures are to be changed or replaced, the piping shall be replaced with appropriate sizes and materials as prescribed for new work.


      Section 13. Prohibited Connections. (1) A fixture connection shall not be made to a lead bend or a branch of a water closet or a similar fixture.

      (2) A vent pipe above the highest installed fixture on a branch or main shall not be used as a soil or waste pipe.


      Section 14. Soil, Waste and Vent Pipe Protected. (1) Soil, waste, or vent pipe shall not be installed or permitted outside a building unless adequate provision shall be made to protect it from frost.

      (2) The piping shall be wrapped with one (1) layer of heavy hair felt and at least two (2) layers of two (2) ply tar paper, properly bound with copper wire, or the vent shall be increased to full size, the size of the increaser required as if it were passing through the roof.


      Section 15. Roof Extensions. (1) A roof extension of soil and waste stacks shall run full size at least one (1) foot above the roof.

      (2) If the roof is used for purposes other than weather protection, the extension shall not be less than five (5) feet above the roof.

      (3) A stack of less than three (3) inches in diameter shall be increased to a minimum of three (3) inches in diameter before passing through a roof.

      (4) If a change in diameter is made, the fitting shall be placed at least one (1) foot below the roof.


      Section 16. Terminals. If a roof terminus of a stack or vent is within ten (10) feet of the top, bottom, face or side edge of a door, window, scuttle, or air shaft, and not screened from the opening by a projecting roof or building wall, it shall extend at least two (2) feet above the top edge of the window or opening.


      Section 17. Terminals Adjoining High Buildings. (1) Soil, waste or vent pipe extension of a new or existing building shall not run or shall not be placed on an outside wall, but shall be installed inside the building unless the piping is protected from freezing.

      (2) If the new building is built higher than the existing building, the owner of the new building shall not locate a window within ten (10) feet of an existing vent stack on the lower building.


      Section 18. Protected Traps and Vents. (1) A fixture trap shall be protected against siphonage and backpressure.

      (2) Air circulation shall be assured by means of an individual vent.

      (3) A crown vent shall not be permitted.


      Section 19. Distance of Trap from Vent. (1)(a) The distance between the vent and the fixture trap shall be measured along the center line of the waste or soil pipe from the vertical inlet of the trap to the vent opening.

      (b) The fixture trap vent, except for a water closet or a similar fixture, shall not be below the dip of the trap, and each ninety (90) degree turn in the waste line of the main waste, soil, or vent pipe shall be washed.

      (c) A fixture trap shall have a vent located with a developed length not greater than that set forth in the table below:

Size of Fixture Drain

(In Inches)


Trap to Vent

1 1/4

2 ft. 6 in.

1 1/2

3 ft. 6 in.


5 ft.


6 ft.


10 ft.

      (2) A fixture branch on a water closet shall not be more than four (4) feet six (6) inches.


      Section 20. Main Vents to Connect at Base. (1) All main vents or vent stacks shall:

      (a) Connect full size at the base of the main soil or waste pipe at or below the lowest fixture branch; and

      (b) Extend undiminished in size through the roof or be reconnected with the main soil or vent stack at least six (6) inches above the rim of the highest fixture.

      (2)(a) Except as provided in paragraph (b) of this subsection, if it becomes necessary to increase the size of a vertical vent stack, the entire stack shall be increased from its base.

      (b) If the height of a stack which does not serve as the main vent is less than forty-five (45) feet, it shall not be required to be increased from its base.


      Section 21. Vents; Required Sizes. (1) The required size of a vent or vent stack shall be determined by the total number of fixture units it serves and the developed length of the vent, interpolating, if necessary, between permissible length of vent given in the following table:


Pipe Size

(In Inches)

Maximum Length

(In Feet)



1 1/4



1 1/2






2 1/2












      (2) Except for a residential installation, if a fixture opening is installed more than twenty-five (25) feet of developed length from the point where it is connected to the main soil or waste system, or, if more than ten (10) feet of vertical piping is used, the vent shall be continued full size through the roof or returned full size to the main vent.


      Section 22. Branch and Individual Vents. A branch or individual vent shall not be less than one and one-fourth (1 1/4) inches in diameter and shall not exceed the maximum length permitted for a main vent.


      Section 23. Vent Pipes Grades and Connections. (1) A vent or branch vent pipe shall be free from drops or sags and be so graded and connected as to drip back to the soil or waste pipe by gravity.

      (2) If a vent pipe connects to a horizontal soil or waste pipe, the vent branch shall be taken off above the center line of the pipe, and the vent pipe shall rise vertically at an angle of forty-five (45) degrees to the vertical, to a point six (6) inches above the fixture it is venting before offsetting horizontally or connecting to the branch, main, waste, soil or vent.


      Section 24. Vents Not Required; Backwater Traps, Subsoil Catch Basin and Basement Floor Drains. (1) A vent shall not be required on a backwater trap, subsoil catch basin trap or a basement floor drain if the basement floor drain branches into the house drain so that measuring along the flow line from the center of the stack, the floor drain shall not be closer than five (5) feet of the stack, nor farther than twenty (20) feet.

      (2) A basement floor drain shall not require an individual vent if it branches into the house drain so that measuring along the flow line from the center of the house drain the basement floor drain shall not be farther than ten (10) feet from the house drain.


      Section 25. When Common Vent Permissible. If two (2) water closets, two (2) lavatories or two (2) fixtures of identical purpose are located on opposite sides of a wall or partition, or directly adjacent to each other within the prescribed distance as set forth in Section 19 of this administrative regulation measured along the center line of the flow of water, the fixtures may have a common soil or waste pipe and a common vent. It shall be vented in accordance with this administrative regulation.


      Section 26. Floor Drain Individual Vent Not Required. (1) A manufacturer's floor drain shall not require an individual vent if placed on a waste line for a floor drain within the prescribed distance of ten (10) feet from the main waste line, or stack, if the base of the stack is washed and the stack or stacks are undiminished through the roof, or connected to a main vent stack.

      (2) An open receptacle may be connected to a floor drain line without being vented if the waste line discharges into a four (4) inch master trap before entering the sanitary sewer system.


      Section 27. Floor Drain. A floor drain or service sink installed on the operational floor level of a sewage and water treatment plant facility which discharges into an open sump and is not connected directly to the sanitary sewage system shall not be required to be trapped or vented.


      Section 28. House Drain Material. A house drain shall be:

      (1) Extra heavy cast iron;

      (2) Service weight cast iron;

      (3) Brass;

      (4) Type (K) or (L) copper;

      (5) Lead;

      (6) ABS or PVC plastic; or

      (7) Duriron.


      Section 29. Indirect Waste Connections. (1) Waste pipe from a refrigerator drain or other receptacle where food is stored or waste water from a water cooled compressor shall connect indirectly with the house drain, soil or waste pipe.

      (2) The drain shall be vented to the outside air.

      (3) The waste pipe shall discharge into an open sink or another approved open receptacle that is properly supplied with water in accordance with this administrative regulation.

      (4) The connection shall not be located in an inaccessible or unventilated area.


      Section 30. Bar and Soda Fountain Wastes. (1)(a) A bar and soda fountain waste, sink or receptacle shall have a one and one-half (1 1/2) inch P trap and branches.

      (b) The main shall not be less than two (2) inches.

      (c) The fresh air pipe shall not be less than one and one-half (1 1/2) inches.

      (d) The main waste line shall discharge into a properly vented and trapped open receptacle inside or outside a building.

      (2) A floor receptor or floor sink may be installed flush with the finished floor if it has a full grate with an attached funnel to receive indirect waste.

      (3) A floor receptor or floor sink installed specifically for the indirect wastes from a tilting braising pan, tilting kettle, or other similar equipment may be installed level with or slightly recessed in the floor if the receptor is equipped with a proper strainer and receives no other indirect waste.


      Section 31. Open Receptacles. Soil or waste piping receiving the discharge from an open receptacle shall be at least six (6) inches above the surface of the ground if it discharges into a septic system.


      Section 32. Refrigerator and Condensate Wastes. (1) A refrigerator or condensate discharge waste pipe shall not be less than:

      (a) One and one-half (1 1/2) inches for one (1) to three (3) openings; and

      (b) Two (2) inches for four (4) to eight (8) openings.

      (2) Each opening shall be trapped

      (3) The waste piping shall be equipped with sufficient cleanouts to allow for thorough cleaning.


      Section 33. Overflow Pipes. (1) Waste from a water supply tank or exhaust from a water lift shall not be directly connected to a house drain, soil, or waste pipe.

      (2) The waste pipe shall discharge upon a roof or into a trapped open receptacle.


      Section 34. Acid and Chemical Wastes. (1) A corrosive liquid shall not be permitted to discharge into the soil, waste or sewer system unless otherwise permitted by this administrative regulation.

      (2) The waste shall be thoroughly diluted or neutralized by passing through a properly constructed and acceptable dilution or neutralizing pit before entering the house sewer.


      Section 35. Laboratory Waste Piping. (1) Laboratory waste piping shall be sized in accordance with this administrative regulation and each fixture shall be individually trapped.

      (2) A continuous waste and vent pipe system may be used, if the waste discharges into a vented dilution pit outside the building with a vent equal to the size of the drain. The vent may be eliminated if the pit has a ventilated cover.

      (3) If a dilution pit is not required and is not used, the fixtures shall be individually vented.

      (4) If construction conditions permit, the base of the stack of the continuous waste and vent system shall be washed by the last fixture opening, and continue full size independently through the roof.

      (5) A fixture branch exceeding more than the distance specified in the table in Section 19 of this administrative regulation from the main shall be revented and the distance shall be measured from the center of the main to the center of the vertical riser.

      (6)(a) A fixture connection shall rise vertically to a height so that the trap shall not be lower than twelve (12) inches from the bottom of the sink.

      (b) Two (2) or more sinks may be connected into a common waste before entering the riser of the continuous waste and vent system, if the fixtures are not more than five (5) feet from the center of one (1) fixture to the center of the other.


      Section 36. Acid Waste Piping. (1) Underground piping for acid wastes shall be:

      (a) Extra heavy salt glazed vitrified pipe;

      (b) Silicon iron;

      (c) Lead;

      (d) Polyethylene pipe and fittings produced and labeled as ASTM D204;

      (e) Polypropylene pipe produced and labeled as ASTM D4101;

      (f) Polypropylene pipe and fittings produced and labeled as ASTM F-1412; or

      (g) Chlorinated Poly Vinyl Chloride (CPVC) Chemical Waste Drainage Systems meeting ASTM F-2618; or

      (h) Other materials approved in 815 KAR 20:020, Section 5.

      (2) Piping for acid wastes and vents above ground shall be:

      (a) Silicon iron;

      (b) Lead;

      (c) Borosilicate;

      (d) Polyethylene pipe produced and labeled as ASTM D-1204-62T;

      (e) Polypropylene pipe produced and labeled as ASTM D-4101-85; or

      (f) Filament-wound reinforced thermosetting resin pipe produced and labeled as ASTM D-2996 (green or poly thread); or

      (g) Chlorinated Poly Vinyl Chloride (CPVC) Chemical Waste Drainage Systems meeting ASTM F-2618.


      Section 37. Special Vents. A flat vent may be allowed if the design of the building prohibits the type of venting required by this administrative regulation.


      Section 38. Basement Floor Drains and Sanitary Sewage Systems. (1) Except for a basement floor drain exempted under subsection (2) of this section, a basement floor drain shall be connected to the house sewer and properly trapped and vented as set forth in this administrative regulation.

      (2)(a) A basement floor drain in a single family dwelling shall not be connected to the house sewer and shall be exempt from this section if, prior to the installation, the local health department or sanitary sewage system board, plant, district, or treatment plant owner notifies the Division of Plumbing, in writing, that connection is detrimental to the functioning of the sanitary sewer system or subsurface system.

      (b) If the drain is not to be connected to the house sewer, the installation shall also be exempt from the waste, trap and venting provisions of the State Plumbing Code. (Recodified from 401 KAR 1:060, 7-5-1978; Am. 6 Ky.R. 134; eff. 1-2-1980; 7 Ky.R. 509; eff. 1-7-1981; 846; eff. 6-3-1981; 9 Ky.R. 834; eff. 2-2-1983; 1238; eff. 6-1-1983; 14 Ky.R. 1129; eff. 1-4-1988; 16 Ky.R. 72; eff. 8-22-1989; 1272; 1590; eff. 8-22-1989; 18 Ky.R. 2722; eff. 4-3-1992; 3537; 19 Ky.R. 411; eff. 8-1-1992; 1192; 1556; eff. 1-4-1993; 22 Ky.R. 1386; eff. 3-7-1996; 23 Ky.R. 2691; 2990; eff. 2-10-1997; 3978; eff. 6-25-1997; 27 Ky.R. 1905; 2796; eff. 3-22-2001; 30 Ky.R. 2393; 31 Ky.R. 88, eff. 8-6-2004; 32 Ky.R. 2367; 33 Ky.R. 408; eff. 9-120-2006; 34 Ky.R. 1239; 1750; eff. 2-1-2008; 35 Ky.R. 2594; 36 Ky.R. 88; eff. 7-29-2009; 35 Ky.R. 2594; 36 Ky.R. 88; 1352; eff. 3-5-2010.)