5.3 Cleanout Size, Location & Clearances

5.3 Cleanout Size, Location & Clearances

The Fundamental Purpose of Cleanouts

Cleanouts are strategically placed, accessible openings in a drainage system fitted with a removable threaded plug or cap. Because residential drainage systems deal with solid waste, hair, grease, and non-flushable items, clogs are an inevitable reality over the lifespan of a home. Cleanouts exist for a single purpose: to allow the insertion of mechanical rodding equipment (such as drain snakes or power augers) to physically clear these blockages. The International Residential Code (IRC) heavily regulates their location, size, and accessibility to ensure that a plumber can reach and clear any potential blockage without destroying finished walls, cutting into floors, or excavating a yard.

Cleanout plugs are typically manufactured from brass or durable plastics. Brass plugs are often used in cast iron systems, while plastic plugs are used in ABS or PVC systems. They feature a raised square head or a countersunk recess to allow a wrench to grip and turn them.

Required Cleanout Locations (IRC Section P3005.2)

The IRC mandates cleanouts at specific points in the drainage network where blockages are most likely to accumulate, or where access is absolutely necessary to reach long runs of pipe.

1. The Building Drain and Sewer Junction

A primary cleanout is strictly required at or near the junction of the building drain (inside) and the building sewer (outside). This critical cleanout provides access to the main sewer line running out to the municipal street connection or the private septic tank. It can be located either inside the building wall (often at the base of the main stack) or outside, typically within 10 feet of the exterior foundation. If located outside, it is often brought up to grade level in a protective box.

2. Changes of Direction (The 45-Degree Rule)

A cleanout is required for any horizontal drainage piping that makes a change of direction exceeding 45 degrees. Sharp turns and sweeps are the most common locations for solid waste and paper to accumulate and cause clogs. For example, if a pipe makes a 90-degree turn using a long-sweep fitting, or two 45-degree fittings placed closely together, a cleanout must be provided at that juncture.

Exception: A cleanout is not required for a single change of direction if the pipe is entirely within a wall or floor space, provided there is an accessible cleanout upstream that can snake through it.

3. Every 100 Feet of Horizontal Run

In horizontal drainage lines, cleanouts must be installed at intervals not exceeding 100 feet. The standard length of a heavy-duty commercial drain auger cable is 100 feet. This rule ensures that no matter where a blockage occurs in a long, straight run of pipe, the mechanical equipment will be able to reach it from the nearest cleanout.

4. Base of Vertical Stacks

A cleanout is required at the base of each waste or soil stack. When falling wastewater hits the bottom of a vertical stack and transitions to horizontal flow via a sweep fitting, immense turbulence and hydraulic jumps occur. This turbulence makes the base of the stack a prime location for blockages. The cleanout allows a plumber to clear the horizontal line moving away from the stack.

[!NOTE] A removable fixture trap (like a slip-joint P-trap under a kitchen or bathroom sink) can legally serve as a cleanout for the immediate unvented drain line it connects to, provided the line is not excessively long, complex, or larger than the trap itself.

Cleanout Sizing Rules

Cleanouts must be physically large enough to accommodate an auger cable appropriately sized for the diameter of the pipe. The rule of thumb in the IRC is straightforward: cleanouts must be the exact same nominal size as the pipe they serve, up to a maximum of 4 inches. For massive pipes larger than 4 inches (which are rare in standard residential but possible in large multi-family), a 4-inch cleanout is considered sufficient for all rodding equipment.

• For a 1.5-inch sink drain line, use a 1.5-inch cleanout.
• For a 2-inch shower branch line, use a 2-inch cleanout.
• For a 3-inch main branch, use a 3-inch cleanout.
• For a 4-inch building drain, use a 4-inch cleanout.
• For a 6-inch main building sewer, a 4-inch cleanout is the maximum required size.

Clearance and Access Dimensions

Installing a perfectly sized cleanout is completely useless if a plumber cannot physically access it or maneuver their heavy equipment into the opening. The IRC specifies strict minimum working clearances directly in front of the cleanout opening.

• Pipes 3 inches and larger: Must have a minimum clearance of 18 inches directly in front of the cleanout to allow ample room for large, heavy-duty rodding machines, the rigid guide hose, and the operator's hands.
• Pipes smaller than 3 inches: Must have a minimum clearance of 12 inches for smaller hand-held or drill-powered augers.

Furthermore, cleanouts must remain permanently accessible. If they are located under a subfloor, in a crawlspace, or behind a finished drywall surface, an access panel or door of sufficient size must be provided. Cleanouts cannot be permanently concealed by drywall, tile, custom cabinetry, or fixed appliances.

Directional Installation Requirements

Cleanouts must be installed so that they open directly in the direction of the flow of the drainage system, or at right angles to it using a sanitary tee or directional wye. This geometric requirement ensures that when a flexible steel cable is inserted, it naturally curves and travels downstream toward the sewer, pushing the blockage out. If a cleanout tee is installed backward, the auger cable would fight against the flow or travel backward up the system, rendering it entirely useless for clearing downstream clogs.