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Disconnect Plumbing — Preparation and Safety Shutdown

Beginner

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How to Install a Garbage Disposal for the First Time · Step 1 of 7

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Begin by shutting off the hot and cold water supply using the shutoff valves located under the sink. Once the water is off, disconnect the drain line by loosening the compression nuts on the P-trap. Place a bucket underneath to catch any residual water.

Goal: Bathroom Sink Removal

  • Have a small bucket or towel ready to catch any water remaining in the drain trap.

Used in this video

  • BucketCatching residual water from the drain trap.
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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.

Transcript
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We've got under the vanity, you've got a hot and cold with supply coming up through the floor. You've got to shut off on each, which is great. It's perfectly plumbed. And you can see that the supply lines continue up here and then it dives into the wall and then turns and goes up to feed the faucet. What we'll do is I'll shut these valves off and I'll cut the water right here. And we also have a drain line to disconnect right here so I'm going to loosen the compression nut right here and another one up at the top. Okay. So now our drain line is disconnected but it's still not going to release that sink from

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