Chapter 5 Traps, Cleanouts and Backwater Valves 5.1 SEPARATE TRAPS FOR EACH FIXTURE a. Plumbing fixtures shall be separately trapped by a water seal trap placed as close as possible to the fixture outlet. b. The vertical distance from the fixture outlet to the trap weir shall not exceed 24 inches. c. Fixtures shall not be double-trapped unless a relief vent is provided between the two traps. d. Fixture designs having integral dual traps within the fixture shall be permitted. EXCEPTIONS: (1) Fixtures that have integral traps. (2) Interceptors in Chapter 6 that provide the required trap seal. Note: Interceptors in Chapter 6 that do not provide the required trap seal shall be provided with a separate trap. (3) A combination plumbing fixture may be installed on one trap provided the waste outlets are not more than 30 inches apart. (4) One trap may be installed for a 2 or 3-compartment sink or up to three (3) lavatories that are immediately adjacent to each other in the same room, and where the trap is centrally located when three such fixtures are installed. (5) No clothes washer or laundry sink shall be discharged to a trap serving a kitchen sink. (6) As otherwise permitted by this Code. 5.2 SIZE OF FIXTURE TRAPS Fixture trap size (nominal diameter) shall be sufficient to drain the fixture rapidly and in no case less than given in Table 5.2. No trap shall be larger than the drainage pipe into which it discharges. Integral traps shall conform to appropriate standards. 5.3 GENERAL REQUIREMENTS FOR TRAPS 5.3.1 Design of Traps Fixture traps shall be self-scouring and shall have no interior partitions except where such traps are integral with the fixture or where corrosion resistant materials of plastic or glass are used. Solid connections, slip joints, or couplings may be used on the trap inlet, trap outlet, or within the trap seal. (See Section 7.4.6.) 2009 National Standard Plumbing Code 79
Table 5.2 MINIMUM SIZE OF NON-INTEGRAL TRAPS Plumbing Fixture Trap Size in inches Bathtub (with or without overhead shower) 1-1/2 Bidet 1-1/4 Clothes washing machine standpipe 2 Combination sink and wash (laundry) sink with food waste grinder unit 1-1/2 (1) Combination kitchen sink, domestic dishwasher, and food waste grinder 1-1/2 Dental unit or cuspidor 1-1/4 Dental lavatory 1-1/4 Drinking fountain 1-1/4 Dishwasher, commercial 2 Dishwasher, domestic (non-integral trap) 1-1/2 Floor drain 2 Food waste grinder, commercial use 2 Food waste grinder, domestic use 1-1/2 Kitchen sink, domestic, with food waste grinder unit 1-1/2 Kitchen sink, domestic 1-1/2 Lavatory, common (private and public) 1-1/4 Lavatory (barber shop, beauty parlor or surgeon s) 1-1/2 Lavatory, multiple type (wash fountain or wash sink) 1-1/2 Laundry tray (1 or 2 compartments) 1-1/2 Shower stall or shower drain (single shower head) 1-1/2 Shower stall or shower drain (multiple shower heads) 2 Sink (surgeon s) 1-1/2 Sink (flushing rim type, flush valve supplied) 3 Sink (service type with floor outlet trap standard) 3 Sink (service type with P trap) 2 Sink, commercial (pot, scullery, or similar type) 2 Sink, commercial (with food grinder unit) 2 NOTES FOR TABLE 5.2 (1) Separate trap required for wash tray and separate trap required for sink compartment with food waste grinder. 5.3.2 Trap Seals Each fixture trap shall have a liquid seal of not less than two inches and not more than four inches. EXCEPTIONS: (1) Interceptors in Chapter 6 that provide the required trap seal. Note: Interceptors in Chapter 6 that do not provide the required trap seal shall be provided with a separate trap. (2) Special conditions such as accessible fixtures, a deeper seal may be required by the Authority Having Jurisdiction 5.3.3 Trap Setting and Protection Traps shall be set level with respect to their water seals and, where necessary, shall be protected from freezing. 80 2009 National Standard Plumbing Code
5.3.4 Building Traps Building traps shall not be installed except where required by the Authority Having Jurisdiction. Each building trap when installed shall be provided with a cleanout and with a relieving vent or fresh air intake on the inlet side of the trap that shall be at least one-half the diameter of the drain to which it connects. Such relieving vent or fresh air intake shall be carried above grade and terminate in a screened outlet located outside the building. 5.3.5 Prohibited Traps a. The following types of traps shall be prohibited: 1. Traps that depend upon moving parts to maintain their seal. 2. Bell traps. 3. Crown vented traps. 4. Separate fixture traps that depend on interior partitions for their seal, except if made from plastic, glass or other corrosion resistant materials. 5. S traps, of uniform internal dimension. 6. Drum traps. b. Hair interceptors, precious metal interceptors and similar appurtenances shall be permitted as required. 5.3.6 Trap Seal Maintenance a. Traps that could lose their seal due to evaporation because of infrequent use shall have accessible means to replenish the trap seal or be connected to a trap primer conforming to ASSE 1018 or ASSE 1044. b. In addition to the priming requirements of Section 5.3.6.a, floor drains shall be permitted to be fitted with a barrier type floor drain trap seal protection device complying with ASSE 1072. 5.4 DRAINAGE PIPE CLEANOUTS 5.4.1 Cleanout Spacing a. Cleanouts in horizontal drainage lines shall be spaced at intervals not exceeding the following values: 4" pipe size or less: 75 feet 5" size and larger: 100 feet b. The distance referred to in Sections 5.4.1a shall include the developed length of the cleanout pipe. 5.4.2 Building Sewer Cleanouts, when installed on an underground building sewer, shall be extended vertically to or above the finished grade level. 5.4.3 Change of Direction a. Cleanouts shall be installed at changes of direction in drainage piping made with 60, 70 and 90 fittings. EXCEPTION: Where there are multiple changes of direction, not more than one cleanout shall be required in 40 feet of run. b. Cleanouts shall not be required where changes of direction are made with one or more 22 1/2 or 45 fittings. 5.4.4 Cleanouts for Concealed Piping Cleanouts for concealed piping shall be extended through and terminate flush with the finished wall or floor; or pits or chases may be left in the wall or floor, provided they are of sufficient size to permit removal of the cleanout plug and proper cleaning of the system. 2009 National Standard Plumbing Code 81
5.4.5 Base of Stacks a. A cleanout shall be provided near the base of each vertical waste or soil stack and located 6 inches above the flood level rim of the lowest fixture on the lowest floor. If there are no fixtures installed on the lowest floor, the cleanout shall be installed at the base of the stack. b. For buildings with a floor slab, a crawl space of less than 18 inches, or where a stack cleanout is not accessible, the cleanout shall be installed in the building drain or building sewer, not more than five feet outside the building wall. c. Rain leaders and conductors connected to a building storm sewer shall have a cleanout installed at the base of the outside leader or inside conductor before it connects to the horizontal drain. 5.4.6 Building Drain and Building Sewer Junctions and the Property Line a. There shall be a cleanout near the junction of a building drain and building sewer either inside or outside the building wall. b. Cleanouts shall be placed in the building sanitary sewer and the building storm sewer at the property line and brought to the surface in accordance with the requirements of the Adopting Agency. 5.4.7 Direction of Flow Cleanouts shall be installed so that the cleanout opens in the direction of the flow of the drainage line or at right angles thereto. 5.4.8 Connections to Cleanouts Prohibited a. Cleanout plug openings in other than drainage pattern fittings shall not be used for the installation of new fixtures or floor drains. b. If a cleanout fitting or cleanout plug opening is removed from a drainage pattern fitting in order to extend the drain, another cleanout of equal access and capacity shall be provided in the same location. 5.4.9 Cleanout Size Cleanout size shall conform with Table 5.4.9. Table 5.4.9 SIZE OF CLEANOUTS Nominal Nominal Piping Size (inches) Size of Cleanout (inches) 1-1/4 1-1/4 1-1/2 1-1/2 2 2 3 3 4 & 6 4 8 & 10 6 12 & 15 8 NOTES FOR TABLE 5.4.9 (1) See Section 5.4.10 for sizes 12" or larger for building sewers. (2) See Section 5.4.13 for cleanout equivalents. 82 2009 National Standard Plumbing Code
5.4.10 Manholes for Large Pipes a. Manholes shall be provided as cleanouts for building sewers 12" size and larger. Manholes shall be provided at every change of size, alignment, direction, grade, or elevation. The distance between manholes shall not exceed 300 feet. b. Manholes may be provided in lieu of cleanouts in underground building sewers, building drains, and branches thereof, 8" size and larger. c. Such manholes shall comply with the requirements of Section 5.4.10a. d. If manholes are installed indoors, they shall have a bolted, gas-tight cover. e. Manhole construction shall comply with the standards of the Authority Having Jurisdiction. 5.4.11 Cleanout Clearances Cleanouts on 3" or larger pipes shall be so installed that there is a clearance of not less than 18" for the purpose of rodding. Cleanouts smaller than 3 inches shall be so installed that there is a 12" clearance for rodding. 5.4.12 Cleanouts to be Kept Uncovered Cleanout plugs shall not be covered with cement, plaster, or any other permanent finishing material. Where it is necessary to conceal a cleanout plug, a covering plate or access door shall be provided that will permit access to the plug. 5.4.13 Cleanout Equivalent Where the piping is concealed, a fixture trap or a fixture with integral trap, removable without disturbing concealed roughing work, shall be accepted as a cleanout equivalent, provided the opening to be used as a cleanout opening is the size required by Table 5.4.9. EXCEPTIONS: (1) The trap arm of a floor drain with a removable strainer. (2) Fixtures with removable traps not more than one pipe size smaller than the drain served shall be permitted. 5.4.14 Cleanouts for Floor Drains A cleanout shall be provided immediately downstream from a floor drain whose strainer is not removable. 5.5 BACKWATER VALVES 5.5.1 Where Required a. Fixtures and/or drain inlets subject to backflow and overflow from blocked or restricted public sewers shall be protected by a backwater valve. b. Such situations include those where the flood level rim of fixtures and/or drain inlets are below the overflow level of the first upstream manhole in the public sewer that will overflow due to a blockage or flow restriction in the public sewer. c. Backwater valves shall be installed in drainage piping that receives flow only from fixtures and/or drains that are subject to backflow from public sewers. d. Other portions of the drainage system not subject to such backflow shall not drain through a backwater valve. 2009 National Standard Plumbing Code 83
5.5.2 Material Standard and Accessibility Backwater valves shall conform to ASME A112.14.1 and be installed so that their internal working parts are accessible for periodic cleaning, repair or replacement. 5.5.3 Notice of the Installation of Backwater Valves When backwater valves are installed in building sanitary drainage systems, a notice shall be posted at the building water service shutoff valve(s) describing where backwater valves are located. 84 2009 National Standard Plumbing Code