Earlier editions: 2022 2019

509.8 Through-the-Wall Vent Termination.

California Plumbing Code (Title 24, Part 5) · 2025 edition · updated 2026-09-10 · California

Italicized text is a California amendment to the model code, as printed in the official publication.

Throughthe-wall vent termination shall be in accordance with Section 509.8.1 through Section 509.8.3.

509.8.1 Clearance for Through-the-Wall Vent Ter- mination. The clearance for through-the-wall direct and non-direct vent terminals shall be in accordance with Table 509.8.1 and Figure 509.8.1.

Exception: The clearances in Table 509.8.1 shall not apply to the combustion air intake of a direct vent appliance. [NFPA 54:12.9.1]

» FIGURE 509.8.1 EXIT TERMINALS OF MECHANICAL DRAFT AND DIRECT-VENT VENTING SYSTEMS

[NFPA 54: FIGURE 12.9.1]

100 2025 CALIFORNIA PLUMBING CODE

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TABLE 509.8.1

THROUGH-THE-WALL DIRECT-VENT TERMINATION CLEARANCES

[NFPA 54: TABLE 12.9.1]

FIGURE CLEARANCE	CLEARANCE LOCATION	MINIMUM CLEARANCES FOR DIRECT VENT TERMINALS	MINIMUM CLEARANCES FOR NON-DIRECT VENT TERMINALS
A	Clearance above finished grade level, veranda, porch, deck, or balcony	12 inches	12 inches
B	Clearance to window or door that is openable	6 inches for appliances ≤ 10 000 Btu/hr	4 feet below or to side of opening or 1 foot above opening
B	Clearance to window or door that is openable	9 inches for appliances > 10 000 Btu/hr≤ 50 000 Btu/hr	9 inches for appliances > 10 000 Btu/hr≤ 50 000 Btu/hr
B	Clearance to window or door that is openable	12 inches for appliances > 50 000 Btu/hr≤ 150 000 Btu/hr	12 inches for appliances > 50 000 Btu/hr≤ 150 000 Btu/hr
B	Clearance to window or door that is openable	Appliances > 150 000 Btu/hr, in accordance with the appliance manufacturer’s instructions and not less than the clearances specified for non-direct vent terminals in row B	Appliances > 150 000 Btu/hr, in accordance with the appliance manufacturer’s instructions and not less than the clearances specified for non-direct vent terminals in row B
C	Clearance to non-openable window	None unless otherwise specified by the appliance manufacturer	None unless otherwise specified by the appliance manufacturer
D	Vertical clearance to ventilated soffit located above the terminal within a horizontal distance of 2 feet (610 mm) from the center line of the terminal	None unless otherwise specified by the appliance manufacturer	None unless otherwise specified by the appliance manufacturer
E	Clearance to unventilated soffit	None unless otherwise specified by the appliance manufacture	None unless otherwise specified by the appliance manufacture
F	Clearance to outside corner of building	None unless otherwise specified by the appliance manufacture	None unless otherwise specified by the appliance manufacture
G	Clearance to inside corner of building	None unless otherwise specified by the appliance manufacture	None unless otherwise specified by the appliance manufacture
H	Clearance to non-mechanical air supply inlet to building and the combustion air inlet to any other appliance	Same clearance as specified for row B	Same clearance as specified for row B
I	Clearance to a mechanical air supply inlet	10 feet horizontally from inlet or 3 feet above inlet	10 feet horizontally from inlet or 3 feet above inlet
J	Clearance above paved sidewalk or paved driveway located on public property or other areas where condensate or vapor can cause a nuisance or hazard	7 feet and not located above public walkways or other areas where condensate or vapor can cause a nuisance or hazard	7 feet and not located above public walkways or other areas where condensate or vapor can cause a nuisance or hazard
K	Clearance to underside of veranda, porch, deck, or balcony	12 inches where the area beneath the veranda, porch, deck, or balcony is open on not less than two sides. The vent terminal is prohibited in this location where only one side is open.	12 inches where the area beneath the veranda, porch, deck, or balcony is open on not less than two sides. The vent terminal is prohibited in this location where only one side is open.

For SI Units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW

509.10.1 Materials. A vent connector shall be made of noncombustible, corrosion-resistant material capable of withstanding the vent gas temperature produced by the appliance and of sufficient thickness to withstand physical damage. [NFPA 54:12.11.2.1]

509.10.1.1 Unconditioned Area. Where the vent connector used for an appliance having a draft hood or a Category I appliance is located in or passes through an unconditioned area, attic, or crawl space, that portion of the vent connector shall be listed Type B, Type L, or listed vent material having equivalent insulation qualities.

Exception: Single-wall metal pipe located within the exterior walls of the building and located in an unconditioned area other than an attic or a crawl space having a local 99 percent winter design temperature of 5°F (-15°C) or higher. [NFPA 54:12.11.2.2]

509.10.1.2 Residential-Type Appliances. Vent connectors for residential-type appliances shall comply with the following:

(1) Vent connectors for listed appliances having draft hoods, appliances having draft hoods and equipped with listed conversion burners, and Category I appliances that are not installed in attics, crawl spaces, or other unconditioned areas shall be one of the following:

(a) Type B or Type L vent material.

(b) Galvanized sheet steel not less than 0.018 of an inch (0.457 mm) thick.

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(d) Stainless steel sheet not less than 0.012 of an inch (0.305 mm) thick.

(e) Smooth interior wall metal pipe having resistance to heat and corrosion equal to or greater than that of Section 509.10.1.2(1)(b), Section 509.10.1.2(1)(c), or Section 509.10.1.2(1)(d).

(f) A listed vent connector.

(2) Vent connectors shall not be covered with insulation.

Exception: Listed insulated vent connectors shall be installed in accordance with the manufacturer’s installation instructions. [NFPA 54:12.11.2.3]

509.10.1.3 Nonresidential Low-Heat Appli- ances. A vent connector for a nonresidential lowheat appliance shall be a factory-built chimney section or steel pipe having resistance to heat and corrosion equivalent to that for the appropriate galvanized pipe as specified in Table 509.10.1.3. Factory-built chimney sections shall be joined together in accordance with the chimney manufacturer’s instructions. [NFPA 54:12.11.2.4]

TABLE 509.10.1.3

MINIMUM THICKNESS FOR GALVANIZED STEEL VENT

CONNECTORS FOR LOW-HEAT APPLIANCES

[NFPA 54: TABLE 12.11.2.4]

DIAMETER OF CONNECTOR (inches)	MINIMUM THICKNESS (inches)
Less than 6	0.019
6 to less than 10	0.023
10 to 12 inclusive	0.029
14 to 16 inclusive	0.034
Over 16	0.056

For SI units: 1 inch = 25.4 mm, 1 square inch = 0.000645 m [2]

509.10.1.4 Medium-Heat Appliances. Vent connectors for medium-heat appliances shall be constructed of factory-built, medium-heat chimney sections or steel of a thickness not less than that specified in Table 509.10.1.4 and shall comply with the following:

(1) A steel vent connector for an appliance with a vent gas temperature in excess of 1000°F (538°C) measured at the entrance to the connector shall be lined with medium-duty fire brick or the equivalent. (2) The lining shall be at least 2 [1] ⁄ 2 inches (64 mm) thick for a vent connector having a diameter or greatest cross-sectional dimension of 18 inches (457 mm) or less.

(3) The lining shall be at least 4 [1] ⁄ 2 inches (114 mm) thick laid on the 4 [1] ⁄ 2 inches (114 mm) bed for a

vent connector having a diameter or greatest cross-sectional dimension greater than 18 inches (457 mm).

(4) Where factory-built chimney sections are installed, they shall be joined together in accordance with the chimney manufacturer’s instructions. [NFPA 54:12.11.2.5]

TABLE 509.10.1.4 MINIMUM THICKNESS FOR STEEL VENT CONNECTORS FOR MEDIUM-HEAT APPLIANCES [NFPA 54: TABLE 12.11.2.5]
VENT CONNECTOR SIZE	VENT CONNECTOR SIZE	VENT CONNECTOR SIZE
DIAMETER (inches)	AREA (square inches)	MINIMUM THICKNESS (inches)
Up to 14	Up to 154	0.053
Over 14 to 16	154 to 201	0.067
Over 16 to 18	201 to 254	0.093
Over 18	Exceeding 254	0.123

For SI units: 1 inch = 25.4 mm, 1 square inch = 0.000645 m [2]

509.10.2 Size of Vent Connector. A vent connector

for an appliance with a single draft hood or for a Category I fan-assisted combustion system appliance shall be sized and installed in accordance with Section 510.0 or

engineering methods. [NFPA 54:12.11.3.1]

509.10.2.1 Manifold. Where a single appliance having more than one draft hood outlet or flue collar is installed, the manifold shall be constructed according to the instructions of the appliance manufacturer. Where there are no instructions, the manifold shall be designed and constructed in accordance with engineering methods. As an alternative method, the effective area of the manifold shall equal the combined area of the flue collars or draft hood outlets, and the vent connectors shall have a minimum 1 foot (305 mm) rise. [NFPA 54:12.11.3.2]

509.10.2.2 Size. Where two or more appliances are connected to a common vent or chimney, each vent connector shall be sized in accordance with Section

510.0 or engineering methods. [NFPA 54:12.11.3.3]

As an alternative method applicable only where all of the appliances are draft hood-equipped, each vent connector shall have an effective area not less

than the area of the draft hood outlet of the appliance to which it is connected. [NFPA 54:12.11.3.4]

509.10.2.3 Height. Where two or more appliances are vented through a common vent connector or vent manifold, the common vent connector or vent manifold shall be located at the highest level consistent with available headroom and clearance to combustible

material and sized in accordance with Section 510.0

or engineering methods. [NFPA 54:12.11.3.5]

For SI units: 1 inch = 25.4 mm, 1 square inch = 0.000645 m [2]

TABLE 509.10.1.3

MINIMUM THICKNESS FOR GALVANIZED STEEL VENT

CONNECTORS FOR LOW-HEAT APPLIANCES

[NFPA 54: TABLE 12.11.2.4]

For SI units: 1 inch = 25.4 mm, 1 square inch = 0.000645 m [2]

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As an alternative method applicable only where there are two draft hood-equipped appliances, the effective area of the common vent connector or vent manifold and all junction fittings shall be not less than the area of the larger vent connector plus 50 percent of the area of the smaller flue collar outlet.

[NFPA 54:12.11.3.6]

509.10.2.4 Size Increase. Where the size of a vent

connector is increased to overcome installation limitations and obtain connector capacity equal to the appliance input, the size increase shall be made at the appliance draft hood outlet. [NFPA 54:12.11.3.7]

509.10.3 Two or More Appliances Connected to a Single Vent. Where two or more openings are provided into one chimney flue or vent, either of the following shall apply:

(1) The openings shall be at different levels.

(2) The connectors shall be attached to the vertical portion of the chimney or vent at an angle of 45 degrees (0.79 rad) or less relative to the vertical. [NFPA 54:12.11.4.1]

509.10.3.1 Height of Connector. Where two or more vent connectors enter a common vent, chimney flue, or single-wall metal pipe, the smaller connector shall enter at the highest level consistent with the available headroom or clearance to combustible material. [NFPA 54:12.11.4.2]

509.10.3.2 Pressure. Vent connectors serving Category I appliances shall not be connected to any portion of a mechanical draft system operating under positive static pressure, such as those serving Category III or Category IV appliances. [NFPA 54:12.11.4.3]

509.10.4 Clearance. Minimum clearances from vent

connectors to combustible material shall be in accordance with Table 509.7.3.4(1).

Exception: The clearance between a vent connector and combustible material shall be permitted to be reduced where the combustible material is protected as specified for vent connectors in Table 509.7.3.4(2). [NFPA 54:12.11.5]

509.10.5 Joints. Joints between sections of connector piping and connections to flue collars or draft hood outlets shall be fastened in accordance with one of the following methods:

(1) Mechanically fastened by means of not less than three sheet-metal screws equally spaced around the joint.

(2) Vent connectors of listed vent material assembled and connected to flue collars or draft hood outlets in

accordance with the manufacturer’s instructions.

(3) Other approved means. {NFPA 54:12.11.6}

509.10.6 Connector Junctions. Where vent connectors are joined together, the connection shall be made with a manufactured tee or wye fitting. [NFPA 54:12.11.7]

509.10.7 Slope. A vent connector shall be installed without any dips or sags and shall slope upward toward the vent or chimney at least [1] ⁄ 4 inch per foot (20.8 mm/m).

Exception: Vent connectors attached to a mechanical draft system installed in accordance with appliance and the draft system manufacturers’ instructions. [NFPA 54:12.11.8]

509.10.8 Length of Vent Connector. The length of vent connectors shall comply with Section 509.10.8.1 or Section 509.10.8.2.

509.10.8.1 Single Wall Connector. The maximum horizontal length of a single-wall connector shall be 75 percent of the height of the chimney or vent, except for engineered systems. [NFPA 54:12.11.9.1] 509.10.8.2 Type B Double Wall Connector. The maximum horizontal length of a Type B double-wall connector shall be 100 percent of the height of the chimney or vent, except for engineered systems. The maximum length of an individual connector for a chimney or vent system serving multiple appliances, from the appliance outlet to the junction with the common vent or another connector, shall be 100 percent of the height of the chimney or vent.

[NFPA 54:12.11.9.2]

509.10.9 Support. A vent connector shall be supported for the design and weight of the material employed to maintain clearances and prevent physical damage and separation of joints. [NFPA 54:12.11.10]

509.10.10 Chimney Connection. Where entering a flue in a masonry or metal chimney, the vent connector shall be installed above the extreme bottom to avoid stoppage.

Where a thimble or slip joint is used to facilitate removal of the connector, the connector shall be firmly attached to or inserted into the thimble or slip joint to prevent the connector from falling out.

Means shall be employed to prevent the connector from entering so far as to restrict the space between its end and the opposite wall of the chimney flue. [NFPA 54:12.11.11.1 – 12.11.11.3]

509.10.11 Inspection. The entire length of a vent connector shall be readily accessible for inspection, cleaning, and replacement. [NFPA 54:12.11.12]

509.10.12 Fireplaces. A vent connector shall not be connected to a chimney flue serving a fireplace unless the fireplace flue opening is permanently sealed. [NFPA 54:12.11.13]

509.10.13 Passage Through Ceilings, Floors, or Walls. A vent connector shall not pass through a ceiling, floor, or fire-resistance-rated wall. A single-wall metal pipe connector shall not pass through an interior wall.

Exceptions:

(1) Vent connectors made of listed Type B or Type L vent material and serving listed appliances with draft hoods and other appliances listed for use with Type

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planes and shall be located so that the relief opening is not obstructed by any part of the appliance or adjacent construction. The appliance and its draft hood shall be located so that the relief opening is accessible for checking vent operation. [NFPA 54:12.13.6]

509.12.6 Clearance. A draft hood shall be located so that its relief opening is not less than 6 inches (152 mm) from any surface except that of the appliance it serves and the venting system to which the draft hood is connected. Where a greater or lesser clearance is indicated on the appliance label, the clearance shall not be less than that specified on the label. Such clearances shall not be reduced. [NFPA 54:12.13.7]