How to Install a Garbage Disposal | Ask This Old House

In this video, Richard Trethewey teaches the process of installing a garbage disposal where there was not one originally.

What Is a Garbage Disposal For?
Garbage disposals are helpful to have because there’s less risk of plumbing drain damage from food going down the pipes, less trash being generated from food waste, and there is reduced kitchen odor from rotting food.

Steps for Installing a Garbage Disposal
People might want to try to install one themselves, so it’s important to understand the basics involved with the installation, particularly the parts and pieces that are needed.
It’s very easy to get confused in the plumbing aisle, so Richard breaks down the various PVC piping and fittings that can be found. These are the steps for how to install a garbage disposal.

Time: 3 hours
Cost: $100—$400
Skill Level: Moderate

Tools:

Shopping List:

Steps:
1. Disconnect the P-trap from the drain tail pipe with a wrench.
2. Cut the P-trap near where it exits the cabinet, which is most likely from the side or the back of the cabinet, with a mini hacksaw. Keep a bucket underneath the P-trap for any waste or sludge that might have built up in the pipes.
3. Disconnect the sink stopper and the tail pipe from the sink, which can be done from underneath with a wrench.
4. Clean the old putty on the top of the sink.
5. Apply plumber’s putty to the bottom of the new sink flange and place it in the drain hole.
6. From underneath, secure the sink flange to the counter. Older models will use three screws that can be tightened with a screwdriver, and many models now use a plastic, hand-tightened ring.
7. If the dishwasher hose needs to drain into the garbage disposal, most models come with a knockout hole that you can punch through to run the hose.
8. Attach the disposal to the mounting ring that’s attached to the sink flange. It usually can twist right on and be hand tightened.
9. Next, connect the P-trap. The hole for the drain line is usually on the side of the disposal, so new drain pipes will need to be run and connected.
10. Seal all the connections for the new P-trap, depending on what type of piping is chosen.
11. Open the faucet and check for any leaks.
12. Plug the disposer into the outlet or call an electrician to wire the disposal to power.

Where to find it?

The other tools and materials he used to install the disposal, including the plumber’s putty, array of PVC piping, fittings, cleaner, and glue, and wrenches can all be found at home centers and plumbing supply houses.

About Ask This Old House TV:
From the makers of This Old House, America’s first and most trusted home improvement show, Ask This Old House answers the steady stream of home improvement questions asked by viewers across the United States. Covering topics from landscaping to electrical to HVAC and plumbing to painting and more. Ask This Old House features the experts from This Old House, including general contractor Tom Silva, plumbing and heating expert Richard Trethewey, landscape contractor Jenn Nawada, master carpenter Norm Abram, and host Kevin O’Connor. Ask This Old House helps you protect and preserve your greatest investment—your home.

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How to Install a Garbage Disposal | Ask This Old House

[AStanton]

A trick I learned from a Lowe's video on disposal installs was, if you are working by yourself, lay the new garbage disposal in the sink on the newly installed basin strainer when you go to tighten up the nut below the sink. The disposal's weight keeps the strainer from rising up/turning. Also use a pair of channel locks to squeeze that locking ring home off one of the points of the disposal. You get better leverage then pushing the ring into place with a screwdriver or whatever other tool.

[benharrison]

It would be a lot easier if all plumbing work, including a Installing a garbage disposal, under the kitchen sink was done at chest high level as shown in this video instead of upside down and backwards as is the work under a typical kitchen sink.

[jakrol]

The air switch is a fantastic tip. I have a cutout for an old soap dispenser we don't use that I could repurpose. I was originally considering making a cutout in the false drawer in the cabinet, or just mount a switch inside the cabinet, but that setup is so much more sophisticated. Great!

[chuckhortler]

Thanks! the small glimpse of sticking a screwdriver through the eyes on the mounting collar were key for me... I'd been sweating and strugging trying to get mine re-mounted by hand and a wrench... screwdriver was magic.

[jimpie]

Here in this area (Cook and Lake Counties, Illinois, Chicago area) to transition immediately out of the wall to the thin wall pvc (not schedule 40). I have never seen the setup you did on this video. It’s very common that sometimes the drain on the wall is higher than the drain on the disposer. A plumber showed me a trick that he uses on this type of installation. Out of the disposer elbow, he reversed the p-trap, then put everything together with Teflon tape and Teflon paste, all thin wall tubing. This is in a rental condo, the fix was done 3 years ago, so far no problems. I worked on this for 3 hours, he came and we were out of there in 15 minutes.
drain works perfectly. The codes in Cook County are one of the toughest plumbing codes in the US. This plumbers specialty was high rise drains.Peter I hope you’re smiling at me, I’m passing along your expertise, God bless you!

[cjhklrv]

I love how they have to crawl in for legs to do the conexions, very realistic and helpful video 😂

[ilovejesus-by]

Thank you for your videos. They are amazing and very helpful! I have a question. I want to remove my old garbage disposal but is wired directly from the electricity. Can you guide me thru how to removed it?

[Slowhand]

Buy 4 of everything you can imagine using. One return trip for returns is better than 8 trips.
#2 dry fit everything . Start a bit long and cut a bit off each time . Then when it’s all perfect dry then glue. You will want to glue twist just a bit and hold for 20 seconds. PVC glue in particular will want to push apart for a few seconds.
Personally I do all drains in ABS because it’s just better.

[The_Return_of_JoyBoy]

I’m a maintenance tech and we have to replace these all the time. Some steps were left out as far as the installation is concerned and that was not a good example of a real world scenario at all.

[whiskeystraw]

That’s back East, here in desert of NW if the disposal don’t line up with drain they just tell ya to build a new house……easy Peezy! Thanks for refresher I like these cause as a owner it’s not my trade and these help it come back from last time I did it! Thanks Guys.

[normrodriguez]

I watch this just to see your technique installing the snap ring .... which you conveniently left out

[Vonn]

Is there a video on how to install the electrical for the disposal?

[virginiamata]

We are trying to Install a disposal on a farm sink but can’t get the snapper on. Any suggestions

[ehmt-]

As a total novice I would have liked to hear more about the glue used and what that air motor was for exactly

[-old-Forthischet]

I finally deleted my garbage disposal last year. I only ran it to verify that it still worked! I just installed a deep sink drain basket with a removable basket and on top of that a separate strainer. Now, no food waste gets down into the drain pipe at all.

[jimtoxford]

I like how his sink cabinet is at chest height. That was the problem all along for probably everybody.

[gibbsm]

Do Not Forget to remove the drain outlet plug for the dishwasher connection. Ask me how I know, LOL.

[StartVisit]

Will be nice to see details on electrical hookup.

[Donteatacowman]

Thanks. I'm moving into an Old House (1910) and would love to put a dishwasher and garbage disposal in at the same time. I probably can't DIY it but I'm trying to figure out how to do it without unnecessary expenses - or to find out if I can't afford to do it yet, conversely. The garbage disposals seem so temptingly affordable and easy

[danielmaldonado]

I never put glue joint ptrap underneath kitchen sink or bathroom cause if you need to get the ptrap off how are you gonna get it off without cutting anything