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Install New Strainer with Plumber's Putty — Install the New Mounting Assembly

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How to Install a Garbage Disposal for the First Time · Step 3 of 7

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Take a small amount of plumber's putty and roll it into a rope about the thickness of a pencil. Apply this rope of putty evenly to the underside of the new sink strainer's flange. Firmly press the new strainer down into the sink drain opening. From underneath the sink, slide the rubber gasket, then the paper friction washer, and finally the large locknut onto the strainer's threads. Hand-tighten the locknut to hold the assembly in place.

Goal: Seat the new strainer in the sink

  • Knead the plumber's putty in your hands to warm it up, making it more pliable and easier to apply.
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This Old House

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FAQs

What are the essential safety steps to take before and during a first-time garbage disposal installation?

Always turn off the power to the sink area at the circuit breaker first to prevent electrical shock. Wear safety glasses to protect your eyes from debris, and use a bucket and rags to manage water spills. Ensure all electrical connections are secure and properly grounded before restoring power.

Beyond the disposal unit itself, what critical tools and materials are often overlooked but necessary for a smooth installation?

Don't forget plumber's putty for sealing the sink flange, a large bucket and plenty of rags (like HDX Microfiber Rags or WYPALL Towels) for catching residual water, and a good flashlight (like the Panther Vision FLATEYE) to illuminate the workspace. While not always included, you may need a specific InSinkErator 3 ft. Power Cord Installation Kit if your unit isn't pre-wired.

How much time should a beginner set aside for this project, and which part is typically the most challenging?

A first-time garbage disposal installation typically takes 2-4 hours, assuming no major plumbing issues. The most challenging parts are often securing the mounting assembly tightly to the sink to prevent leaks, and making proper, safe electrical connections if you're wiring it yourself rather than just plugging it in.

What are the most common mistakes first-time installers make, and how can I avoid them, especially regarding leaks?

Common mistakes include not applying enough plumber's putty around the sink flange, forgetting to remove the dishwasher knockout plug (if connecting a dishwasher), or not tightening the mounting bolts evenly. To avoid leaks, ensure all connections are hand-tightened and then carefully finished with pliers, and always double-check by running water through the sink for several minutes before buttoning everything up.

Install New Strainer with Plumber's Putty — How to Install a Garbage Disposal for the First Time (Step 3, Video 2) | Stesso