4.3 Cleanout Sizing, Locations, Clearances & Installation Standards

4.3 Cleanout Sizing, Locations, Clearances & Installation Standards

Quick Answer: Cleanouts are mandatory maintenance access points in sanitary drainage systems governed by NC Plumbing Code Section 708. Cleanouts must be installed at the base of every vertical stack, at the junction of the building drain and sewer (inside or outside within 10 feet of the foundation), at horizontal changes of direction greater than 45 degrees, and along horizontal runs at intervals not exceeding 100 feet. Cleanouts must be equal to pipe size up to 4 inches; for pipes larger than 4 inches, a 4-inch cleanout is code-compliant. Required unobstructed front clearances are 18 inches for pipes $\le 2"$ and 24 inches for pipes $\ge 3"$. Cleanouts must open in the direction of flow and cannot be used as fixture drains.

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Mandatory Cleanout Locations (NCSPC Section 708.1)

To ensure sewer cables, kinetic water jetters, and diagnostic inspection cameras can access all internal drainage surfaces, the North Carolina Plumbing Code dictates strict cleanout placement:

+-------------------------------------------------------------------------+
|                   MANDATORY CLEANOUT LOCATIONS                          |
+-------------------------------------------------------------------------+
|                                                                         |
|  [LOC 1: BASE OF VERTICAL STACK]                                        |
|          │                                                              |
|          ├── (Cleanout tee with raised/countersunk plug)                |
|          ▼                                                              |
|     ┌──────────┐                                                        |
|     │ ╰─────── │                                                        |
|     └──────────┘                                                        |
|                                                                         |
|  [LOC 2: CHANGE OF DIRECTION > 45°]                                     |
|          Horizontal Run ─────────► [Wye Cleanout] ───► (Turn > 45°)     |
|                                                                         |
|  [LOC 3: 100-FT HORIZONTAL INTERVAL]                                    |
|          ◄────────────────────── 100'-0" MAX ─────────────────────►     |
|          [Cleanout] ──────────────────────────────────── [Cleanout]     |
|                                                                         |
|  [LOC 4: BUILDING DRAIN / FOUNDATION JUNCTION]                          |
|   ═══════════════════════════════════════════════ Building Foundation   |
|          [Inside Cleanout]  OR  [Outside Two-Way Cleanout ≤ 10 ft]      |
|                                                                         |
+-------------------------------------------------------------------------+

The 5 Mandatory Cleanout Locations:

1. Base of Vertical Stacks:
   • A cleanout must be provided at or near the foot of each vertical waste or soil stack.
   • Located above the flow line of the horizontal drain, typically 12 to 24 inches above finished floor level.
2. Building Drain / Building Sewer Junction:
   • Near the junction of the building drain and the building sewer.
   • May be located inside the building near the foundation exit wall, or outside the building within 10 feet (3,048 mm) of the exterior foundation wall.
3. Changes of Direction Greater than 45 Degrees:
   • A cleanout is required at each horizontal change of direction exceeding 45 degrees ($1/8$ bend).
   • Exception (Aggregate Changes of Direction): If a horizontal run makes multiple directional changes totaling up to 135 degrees (e.g., three 45° bends), a single cleanout is permitted if the developed length between bends does not exceed 40 feet.
4. 100-Foot Horizontal Spacing Limit:
   • Cleanouts must be installed along horizontal building drains and building sewers at intervals of not more than 100 feet (30,480 mm) measured along the developed centerline of the piping.
5. Manholes on Large Sewers (NCSPC 708.1.2):
   • For building sewers 8 inches and larger, underground concrete manholes may be installed in lieu of standard cleanout fittings at intervals not exceeding 400 feet, at every change of direction, and at all branch intersections.

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Cleanout Sizing Standards (NCSPC Table 708.1.5)

Cleanouts must be sized proportionally to the drainage piping to permit full-diameter sewer rodding blades and jetting heads to pass through without binding.

Master Cleanout Sizing Table

Core Sizing Principle: Cleanouts must be the same nominal size as the pipe for all piping up to and including 4 inches. For piping larger than 4 inches, the cleanout size is capped at 4 inches minimum because 4-inch sewer snakes and jetting nozzles provide sufficient clearing power for 5-inch, 6-inch, and 8-inch lines.

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Working Clearances & Installation Accessibility

Cleanouts must be positioned where plumbers can maneuver heavy motorized drain cleaning machines, flexible cables, and water jet hoses without structural interference.

+-------------------------------------------------------------------------+
|                    CLEANOUT WORKING CLEARANCES                          |
+-------------------------------------------------------------------------+
|                                                                         |
|  CLEANOUTS ≤ 2 INCHES                  CLEANOUTS ≥ 3 INCHES             |
|                                                                         |
|     ┌───────────┐                         ┌───────────┐                 |
|     │ Wall /    │                         │ Wall /    │                 |
|     │ Stack     │                         │ Stack     │                 |
|     │    ┌─┐    │                         │    ┌─┐    │                 |
|     │    │ │ ◄── Cleanout Plug            │    │ │ ◄── Cleanout Plug    |
|     │    └─┘    │                         │    └─┘    │                 |
|     └─────┬─────┘                         └─────┬─────┘                 |
|           │                                     │                       |
|           ◄────── 18" MINIMUM ──────►           ◄────── 24" MINIMUM ────|
|                Front Clearance                       Front Clearance    |
|                                                                         |
+-------------------------------------------------------------------------+

Code Clearance Dimensions (NCSPC 708.1.4)

1. Piping 2 Inches and Smaller: Must maintain a minimum unobstructed front working clearance of 18 inches (457 mm).
2. Piping 3 Inches and Larger: Must maintain a minimum unobstructed front working clearance of 24 inches (610 mm) (18 inches absolute IPC minimum; 24 inches required in North Carolina enforcement for power cable clearance).
3. Concealed Piping & Access Panels: Cleanouts concealed inside finished drywall, masonry, or tile walls must be brought flush to the finished wall surface with an extended cleanout adapter, or made accessible through a hinged access panel measuring not less than $12 \times 12\text{ inches}$.
4. Under-Floor / Slab Cleanouts: Cleanouts located below concrete slabs or finished floors must be extended vertically to finished floor grade using an approved adjustable floor cleanout assembly equipped with a gas-tight countersunk plug and a heavy-duty scoriated (non-slip) access cover plate.
5. Crawlspace Cleanouts (NCSPC 708.1.3): Cleanouts installed in under-floor crawlspaces must be located within 20 feet of the crawlspace access entry door, or the crawlspace must provide an unobstructed walking/crawling passageway with a minimum vertical clearance of 24 inches and minimum horizontal width of 30 inches.

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Cleanout Plugs, Fittings & Two-Way Cleanouts

1. Cleanout Plug Styles & Materials

• Plug Materials: Cleanout plugs must be constructed of heavy cast brass or approved plastic (PVC/ABS) matching the piping material, complying with ASTM standards.
• Raised Square Nut Head: Standard for exposed wall cleanouts, basement stack bases, and yard cleanouts where a wrench can grip the exterior raised lug.
• Countersunk Slotted / Hex Head: Mandated for floor cleanouts, walkways, and traffic areas. The plug sits completely flush with the top ferrule, requiring a socket or cleanout key to remove, eliminating tripping hazards and vehicular tire damage.

+-------------------------------------------------------------------------+
|                    PLUG STYLES & TWO-WAY CLEANOUTS                      |
+-------------------------------------------------------------------------+
|                                                                         |
|    RAISED SQUARE HEAD                   COUNTERSUNK FLUSH HEAD          |
|    (Exposed walls / basements)          (Floor / Traffic surfaces)      |
|          ┌──┐                                 ┌──────┐                  |
|          │  │ ◄── Wrench Lug                  │ ──┴──│ ◄── Hex Socket   |
|       ┌──┴──┴──┐                           ┌──┴──────┴──┐               |
|       │ Thread │                           │   Thread   │               |
|       └────────┘                           └────────────┘               |
|                                                                         |
|    TWO-WAY CLEANOUT TEE (Yard Cleanout at Building Perimeter)           |
|                            │ Upright Access Pipe                        |
|                            ▼                                            |
|                       ┌─────────┐                                       |
|       To Sewer ◄───── │ ╰──┬──╯ │ ─────► To Building Drain             |
|       (Downstream)    └────┴────┘        (Upstream)                     |
+-------------------------------------------------------------------------+

2. Two-Way Cleanouts (Yard Cleanouts)

• Installed on the exterior building sewer within 10 feet of the building foundation.
• Features a symmetrical double-sweep curved fitting (or back-to-back wyes) extending to grade.
• Function: Allows a plumbing technician to run a snake upstream (back into the building drain) to clear interior blockages, or downstream (out to the municipal sewer main) to clear root intrusions and sewer main stoppages.

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Directional Flow & Code Prohibitions

Required Direction of Opening (NCSPC 708.1.7)

• Cleanout openings must be oriented in the direction of drainage flow (using a 45° wye or combo) or at right angles ($90^\circ$) to the flow line (using a tee-wye / cleanout tee).
• Cleanouts must never be installed facing backwards against the flow of wastewater.

Prohibited Cleanout Practices

1. Repurposing as Fixture Drains: A cleanout opening cannot be used as a connection point for a new fixture drain, floor drain, or condensate line. Connecting a drain to a cleanout fitting voids its legal status as a cleanout.
2. Concealment Without Access: Encasing a cleanout fitting in solid concrete, dry-walling over a cleanout without an access panel, or burying an exterior cleanout in landscape dirt without a protective valve box is a major code violation.
3. Thread Reducers: Reducing the size of a cleanout plug below the required code diameter (e.g., using a bushing to fit a 2-inch plug into a 3-inch cleanout tee) is strictly prohibited.

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Exam Traps & Pro-Tips

[!WARNING] Common Exam Pitfall #1 — Cleanout Sizing on Large Piping: An exam question will ask: "What size cleanout is required for a 6-inch horizontal building sewer?" Options will include 6-inch, 4-inch, 3-inch, and 2-inch. The correct answer is 4 inches. Cleanouts do not need to exceed 4 inches on piping larger than 4 inches.

[!IMPORTANT] Exam Pro-Tip #2 — 100-Foot Interval Rule: The maximum permissible developed length between cleanouts on any straight horizontal drainage run is 100 feet.

[!TIP] Exam Pro-Tip #3 — Countersunk Plugs: Always select countersunk plugs for floor installations, parking decks, and finished walkways. Raised head plugs are prohibited in floors because they create dangerous pedestrian trip hazards.