Therwen 3.5-Inch Brass Cleanout Cap 2-Pack — Slotted Concave Head, Threaded Leak-Resistant Seal

Therwen's 2-piece slotted 3.5-inch brass cleanout cap is a durable, threaded sewer cleanout plug designed to seal 3.5-inch drain or vent openings securely while allowing easy removal with a standard slotted wrench.

This two-pack of brass cleanout caps fits 3.5-inch threaded tubing and combines a countersunk head with machine thread and a square groove to deliver a reliable, leak-resistant seal. Made from solid brass, each plug is built to resist corrosion and stand up to typical environmental stresses encountered in plumbing systems. The slotted head permits quick access for routine maintenance, while the included design features help prevent odors and gas seepage when installed properly.

How do these cleanout caps protect my drain and piping?

When threaded into a 3.5-inch cleanout opening, the brass cap forms a tight mechanical barrier that minimizes the escape of sewer gases and blocks debris from entering the piping. Brass material resists rust and physical wear, maintaining the integrity of the seal over time with normal use.

• Creates a secure threaded seal to reduce leak and odor pathways
• Countersunk head sits flush with piping to limit snagging and debris build-up
• Square groove and machine thread provide reliable torque transfer for tight installation
• Durable brass construction reduces corrosion-related failure

Will these caps fit my existing cleanout—what size and design should I check?

These plugs are engineered for 3.5-inch threaded tubing with a countersunk head profile; confirm your cleanout’s thread diameter and pitch before ordering. The plug’s slotted head and square groove are compatible with common plumbing tools, but matching the thread size is the essential step.

• Designed specifically for 3.5-inch threaded cleanout openings
• Check thread diameter and pitch against your fitting for compatibility
• Countersunk head keeps the cap flush for a tidy installation
• Slotted design accepts standard screwdriver or wrench for removal

How do I install and remove these brass cleanout plugs safely?

Installation is straightforward: thread the cap into the cleanout bore by hand until snug, then use a slotted tool or compatible wrench on the head or square groove to tighten. For removal, back the plug out with the same tool while taking care to avoid cross-threading or over-torquing, which could damage the threads.

• Hand-start threads to avoid cross-threading, then finish with a slotted driver or wrench
• Tighten until snug; avoid excessive force to protect threads
• Use the square groove for added grip if the slotted head slips
• Inspect thread and seat for debris before reinstallation to ensure a good seal

What maintenance or longevity can I expect from brass cleanout caps?

Brass resists common forms of corrosion that affect steel, so these caps typically offer long service life under normal plumbing conditions. Periodic inspection and cleaning of the threads and seating area will help maintain the seal and make future removals easier.

• Corrosion-resistant brass extends useful life in most environments
• Occasional inspection prevents buildup and keeps the cap accessible
• Replace if threads become damaged or if the cap no longer seals effectively
• Store spare caps dry to prevent surface tarnishing before use

Who is this for: The Therwen 3.5-inch slotted brass cleanout caps are aimed at homeowners, DIYers, and professional plumbers needing a dependable, easy-to-remove seal for 3.5-inch piping cleanouts. They suit routine maintenance, temporary or permanent sealing of drain, waste, and vent access points, and installations where a corrosion-resistant, threaded closure with quick-access removal is preferred.