How To Plumb A Double Kitchen Sink With Disposal And Dishwasher

How to plumb a double kitchen sink with disposal and dishwasher
How to plumb a double kitchen sink with disposal and dishwasher

Plumbing a sink can take a while when you don’t have much experience but it’s an easier installation than most. A combination of disposal and dishwasher is possible even with a single sink, so, a double sink should be no problem at all. Installing a garbage disposal will make cleaning up after a meal much easier. You won’t have to worry about food matter clogging the sink. They will be broken down by the disposal system. The only problem is, you don’t know how to plumb a double kitchen sink with a disposal and dishwasher. Read our guide to find out how to get the job done.

You can install a garbage disposal and dishwasher on your double kitchen sink as long as the following things are alright with it.

  • There has to be enough space underneath the sink to fit the garbage disposal and dishwasher of your choice.
  • Accommodation for pipes connecting your dishwasher and disposals is also necessary.
  • Scope for electric wiring on the underside of your sink will allow you to lead a connection above the sink to a switch for powering the garbage disposal on and off.
  • There is only a slight possibility that your sink won’t be compatible with standard flanges. In that case, you will be fine after getting yourself extended flanges to install the garbage disposal.

How Much Is Installing a Garbage Disposal & Dishwasher Going To Cost?

The cost of a garbage disposal unit can range from $85-200. While dishwashers are more expensive at about $250-3500. However, on average people spend close to $1000 on dishwashers.

If you purchase a mid-range dishwasher from Home Depot worth more than $396, they will install it free of cost. So, it is a good idea to buy both your garbage disposal and dishwasher at the same time to avail this free service.

However, in case you are out of that option, hiring a professional will increase your costs a lot. A professional installation can cost anywhere from $100-$450. In case you have the pre-existing infrastructure, it will cost you on the lower end of this range. The more adjustments the professional needs to make, the more it will cost you.

On the other hand, you can DIY install it, which may require as little as $20. Our step-by-step guide is just what you need to help you with the process.

How Long Does It Take To Install a Garbage Disposal & Dishwasher On a Double Kitchen Sink?

The time it will take you to plumb your sink with a garbage disposal and dishwasher depends on how experienced you are with plumbing. Another major factor is how compatible your sink is with the units you want to install. Some sinks may come with built-in infrastructure, while others may require some adjustments.

Let’s say the level of complexity is basic, then according to the skills you possess, this is how long it should take you to complete the task based on our estimations.

Skill Level

TIme Taken


4 hours – 8 hours

Frequent DIYer

2 hours – 5 hours

Professional Plumber

1 hour – 4 hours

A Step-By-Step Guide On How To Plumb A Double Kitchen Sink With Disposal And Dishwasher

You could be working with a new sink or one with a previously installed garbage disposal or dishwasher, or both. You can have a prepared drainage system or you may need to work out the piping. Based on that we have broken this process into separate installations.

First, we will take a look at how to install a garbage disposal onto a double kitchen sink, then we will share the process of installing a drainage system with a garbage disposal already in place. Lastly, we will look at how to install a dishwasher with your garbage disposal.

Parts of our guide may not apply to you as you may have those systems already in place. That’s fine, you can move on to the next installation.

How To Plumb A Double Kitchen Sink With Garbage Disposal

There’s absolutely no reason for you to be intimidated by this process. Following along with our guide is an easy way to get the job done. Here are the things that you need to get started.

What You Need

  • Bucket
  • Towel
  • Plumber’s Putty
  • Metal scraper
  • Screwdriver
  • Hammer
  • New Flange (May be optional)
  • Hacksaw (May be optional)


Step 1: Preparing To Install The Garbage Disposal

When working with an uninstalled sink, attach the disposer to the sink before placing the sink into place as it allows better access. Otherwise, grab a bucket and some towels to work underneath the sink. Reading the installation instructions for your unit is a good idea.

Step 2: Removing The Old Disposal System If There’s One

For an existing garbage disposal system, turn off the power and unplug it. In case your disposal is hardwired, uncover the access panel to undo the wire connections.

Close the valve supplying water to the sink. Remove the drain pipe. Be ready to catch water in your bucket while doing so. Take off the drain tube from the dishwasher if there’s one.

Use a screwdriver to pry the old disposal from the locking ring and unlatch it. Carefully, bring the old disposal down.

Step 3: Installing A New Sink Flange

You may not need this step if you already have the right kind of flange for your unit and it is in good condition. In that case, skip it.

Start by loosening the mounting screws and prying out the mounting ring. Remove the top part of the flange from above the sink and clean up the old putty. Before replacing it with the new flange, apply a fresh plumber’s putty on it. To let it dry, cover it with a towel and place something heavy to press it.

Now comes the new mounting ring. There are two systems; three bolts and EZ mount. You can just simply screw on the EZ mounting flange by twisting it. Three bolts require putting on a new gasket with the mounting ring and tightening the snap ring. After that, screw the three bolts into place to secure the flange.

Step 4: Installing The New Disposal

Since you will be installing a dishwasher or already have one, remove the knockout plugs to attach them to the drain from your dishwasher. Use a hammer and screwdriver to tap on it.

Hardwire the disposal as per instructions from the owner’s manual or attach electrical wires as needed. Lifting the new unit so you can align it with the mounting flange and slide the locking ring in place with a screwdriver.

Reattach the disposal with drain pipes if you have them or keep on reading to learn how to install the drainage next. You may need to adjust any existing drain pipes to size anyway by cutting them down with a hacksaw or getting a longer one.

Step 7:  Finishing Touches

Clean the excess putty with the scraper. Place the bucket under the new disposal and turn the water on to test for leakage. Turn the power on after plugging in your new disposal.

How To Install Drainage for Garbage Disposal On Double Sink

This process is fairly simple. You don’t need many tools or experience with plumbing for this one. Just follow the steps given below.

  1. Remove the tailpiece nut from the sink strainer. First, pass the tailpiece washer and then the nut along the pipe. Screw the nut tightly by hand.
  2. Mark on the tailpiece after aligning the tee with the disposal outlet. Unscrew the tailpiece and use a hacksaw to cut it to size.
  3. Reinstall the tailpiece. You need to tighten its nut and washer on the sunk strainer.
  4. Slide a slip joint nut and then a slip joint washer on the tailpiece. Hand-tighten the pieces to attach the tee to the tailpiece.
  5. Next, align the disposal outlet with the side inlet of the tee. Use the tailpiece that’s longer to place the flanged end on the outlet of the disposal. Mark the length required to connect the tee. With a hacksaw, cut to size.
  6. You now need the rubber disposal washer. Place it on the flanged end and slide the disposal’s mounting flange up the tailpiece. Next, goes a slip joint nut with a washer that needs to be hand-tightened.
  7. Now, align the tee and tailpiece with the outlet of disposal. Finally, attach the tailpiece to the garbage disposal. Secure the mountain flange and inspect that all the tees are well connected.
  8. Slide one last slip joint nut and washer to secure the tee to the p-trap by hand-tightening. Use the connection piece as per your garbage disposal unit to finalize the installation.

How To Install A Dishwasher With A Sink That Has A Garbage Disposal?

This is the last installation you will be making, after that your double kitchen sink will be ready for use with a garbage disposal and dishwasher in place.

Step 1:

Disconnect the power at the circuit breaker or fuse box and close the water supply valve. You need to start by knocking out the drain plug on your garbage disposal if you saved that part for later when installing the disposal.

Step 2:

Feed a retainer clamp to the drain hose before connecting the hose with the disposer and drain pipe. Ensure that the drain hose is positioned above the connection point in a loop.

Step 3:

The connection point has to be 20 inches above the ground. If not, use an air gap. This will prevent water from re-entering the dishwasher from the drainpipes.

Step 4:

Now, plug in the dishwasher. Make sure you are connecting to an outlet that serves the required voltage. Don’t use any extension cords or adapters. Turn the power and water supply on to test the dishwasher for leakage.

Step 5:

To finish up, replace the inner access panel and then the toe kick panel against the frame. Align the slots with the panels in a way that you can screw them tight. When you are done threading the mounting screws and they are secured, your dishwasher will be ready for use.

This is how you plumb a double kitchen sink with a disposal and dishwasher.

What To Do When The Garbage Disposal Is Letting Waste Into The Dishwasher?

This is an issue that homeowners face frequently when they implement the above sink setup. Instead of calling in a professional that will cost you at least $100, you can try to solve the issue yourself.

Waste being backed into the dishwasher can be a result of leakage in a drain hose that is linking your dishwasher and garbage disposal unit. When there’s a clog in your garbage disposal, water actually goes in the opposite direction than it’s supposed to. Thus ending up in your dishwasher, along with the waste.

The easiest way to solve this issue is to pour boiling hot water on your kitchen sink. When it passes your garbage disposal drain, the accumulated trash and food waste will run down the drainage system. Doing this once a week is a good idea to prevent this issue from happening.

Another possibility is that there is something wrong with the air gap. Inspect it and install a new one if necessary.


With one exception: there may be a sink on each end of the counter if the middle of the counter is blocked or has a separate bar area that needs to have an extra sink for prep work. As far as how the disposals are installed, you’ll want to make sure they’re both facing the same direction.

In general, yes. Installing a garbage disposal involves both an electrical and mechanical hookup, so a professional plumber best handles this type of project. However, sometimes the sink flange can be attached to the disposal unit without a plumber’s help – it just depends on your comfort level with plumbing repairs. If the pipes in your house are too old or you don’t have enough room to handle the job, hire a plumber to do the work for you.

There will be garbage disposals that grind food waste into small particles. Depending on the dishwasher you have, your garbage disposal can affect the way it cleans your dishes. In order to prevent your dishwasher from overflowing, you should not use your garbage disposal. Allowing the water in your dishwasher to drain through the sink will result in excess of food particles that could clog the drain.

Related Article: Best Garbage Disposal for Rental Property

Yes, you can replace a double kitchen sink with a single one. You will need to measure your new sink before ordering it. Place the new sink on top of the counter where you intend to put it. Then determine how much overhang you need on each side. Will you be able to install this yourself? The installation is pretty straightforward. It takes about an hour for the double sink installation and slightly more time for the single sink installation.

Removing a kitchen sink can be challenging. The most crucial thing to consider is to protect the countertop with plenty of padding around the edges of the sink and under the sink itself so that you don’t chip or scratch the countertop when removing the sink. If you do not have the option of removing the sink through the back, using pliers to remove the drain assembly can also work.
It’s simple: Garbage is going to start building up in your house. The floor around the sink will probably be littered with trash, and you’ll have to use a dustpan and a broom to keep it from spreading into the rest of the room. You’ll also find trash inside the garbage disposal itself, which means you’ll have to clean out the drain pipe, too. It’ll take more work and be a lot less convenient than using a garbage disposal.

Final Words

As you can see the process of installing a disposal and dishwasher is a long one but the steps are easy to follow. You don’t need that many tools and DIYing the installation will save you a lot of money.

Having an optimized sink with a disposal and dishwasher will help you free up a lot of time and be super convenient. So, it’s definitely worth the hassle.

Hopefully, our guide on how to plumb a double kitchen sink with disposal and dishwasher has helped you out. If you have questions, you can comment below. We will try our best to clear them for you.

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