How to Plumb a Double Kitchen Sink With Disposal and Dishwasher

Everyone who’s ever maintained a kitchen knows that there’s nothing more annoying than constantly dealing with food waste.

Let’s face it; it doesn’t matter how old you get, taking out food scraps by hand is simply disgusting. But if you want to avoid the possibility of having your kitchen sink clogged up; you simply have to deal with that issue somehow.

So, have you grown tired of scraping remainders of a once-tasty dish into your garbage bin?

Not to mention all the times when you mess up a meal and have to remove the over-cooked food from the bottom of the pans and pots.

If you want all of these problems to go away, a singular solution presents itself — installing a garbage disposal. Having this combined with your sink is simply the best possible thing you can do in such a situation.

However, knowing how to plumb a double kitchen sink with disposal and dishwasher is not always simple. Luckily for you — we’re going to tell you all about this right here!

Why install a garbage disposal system

Garbage disposal beneath the sink is one of the staples of most contemporary kitchens. And if you don’t have one by now; you should know all of the benefits of installing one.

First of all, a garbage disposal can break up any remains of food that end up in your sink and its drain; thus, not only will you do the dishes more quickly, but you also won’t have to deal with as much clogging.

If you care about environmental friendliness, this is an excellent thing to have as well. If you manage to break up more food waste and let it go down your sink, it will be disposed of more easily through sewage; thus reducing the quantity of the trash that ends up in landfills.

Plus, the more food you can put in your garbage disposal, the less food you’ll throw out. In urban areas, that means attracting fewer rats and rodents to your apartment.

And in suburban areas, you won’t have to worry about any wildlife going through your trash after being attracted by the smell of the food waste.

Another great benefit of garbage disposal beneath your kitchen sink is the fact that you won’t have to deal with the damage that big chunks of food waste can do to your plumbing; thus, there will be a lower frequency of plumbing incidents that you need to worry about, and repairs to make.

Can I plumb a double kitchen sink with disposal and dishwasher?

If you wanted to install a garbage disposal and dishwasher unit in a single sink, you could do that as well; so doing it with a double kitchen sink is more than possible.

All you need to do first is to ensure that you’ve got enough space beneath the sink to fit everything. Also, the piping for your sink and the dishwasher and disposal has to fit perfectly as well.

You also need to be sure that you have electric wiring beneath your sink; this will allow you to connect both the dishwasher and the garbage disposal unit once you install them.

This wiring should lead somewhere above the sink on the other side; ideally, a wall switch where you’ll turn the disposal on and off.

Though, you need to bear in mind that there are sinks that aren’t compatible with garbage disposal units. These days, those are a minority; but it’s a possibility that you have to consider.

For instance, there are plenty of thick farmhouse sinks which aren’t compatible with standard flanges. In order to use those with garbage disposals, you’ll need to get an extended flange.

The expenses of installing a garbage disposal

Installing a garbage disposal

There’s a variety of stuff that you’ll need to pay for before plumbing a double kitchen sink with a disposal and dishwasher. First of all, the garbage disposal unit itself.

Naturally, the cost here will largely depend on the type of model and brand that you use. The price can vary wildly, from $90 to more than $200.

Though, if you’re going to install it yourself, you will be saving a lot of money. Dependable plumbers that are guaranteed to do a good job could charge you just as much for installing the units.

Don’t worry, though — as you’ll see from our tutorial here, installing and plumbing this appliance is fairly simple; with some dedication and carefulness, there’s no reason why you shouldn’t be able to do it on your own.

Of course, if you do find that this is too much for you at any time — just contact a professional, and they’ll finish the job easily!

How to install a garbage disposal on a double-bowl sink

For the process of installing this garbage disposal unit, there are a couple of things that you will need:

  • An old rag or piece of cloth
  • Utility knife
  • Hammer
  • Screwdriver
  • Plumber’s putty
  • A putty knife (plastic one)
  • Slip-joint pliers
  • Non-contact voltage tester
  • Wire nuts
  • Wire strippers
  • Your garbage disposal unit

Once you gather everything that we’ve outlined above, bear in mind that this installation process will take you at least a couple of hours.

Then, you may begin:

  1. Make sure that the kitchen cabinet below the sink is clear and clean so that you can maneuver around it and freely work.
  2. Now you can take a look at the circuit breaker for the wiring of your disposal unit, and switch it off.
  3. You need to make sure that there is absolutely no electricity going through the wiring intended for the garbage disposal. Take the voltage tester and see if you’ve switched off the breaker correctly. If there’s still a light on the tester after that, there is still electricity present and you need to switch off all the breakers methodically until there is no power shown by the tester.
  4. Take your slip-joint pliers. Then, use them to remove the couplers that join the extension pipe of the drain and the p-trap with the underbelly of the sink. After that, place all of these drain sections somewhere safe. Also, we advise using the piece of cloth to plug your drainage because it’s bound to release a foul smell around the kitchen otherwise.
  5. Next up, use your pliers to undo the nut that resides below the drain coupling. When you feel that it’s sufficiently loose, push it up and you’ll be able to separate the flange of the drain from the lower part of the sink.
  6. There’s bound to be some residue of the plumber’s putty left on the drain hole from when it was first set up. Take the putty knife and proceed to scrape it off; you won’t be able to fit everything back otherwise.
  7. Take the new putty and rub some of it around the flange of the garbage disposal unit. After that, you can insert this flange into the appropriate hole on your sink.
  8. Take the mounting ring and appropriately snap it into place. Then, proceed to use the screwdriver to tighten any screws; in the end, the disposal unit should be firmly situated beside your sink drain.
  9. Use a rag to wipe away any plumber’s putty that’s in excess.

Just keep in mind that there are plenty of different models of garbage disposals out there.

That means that the process which we’ve described above may differ, especially depending on the type of fitting that the unit uses. However, this is pretty much the basic process that you’ll probably go through.

If you need some additional information, there’s bound to be a user manual with the garbage disposal unit which you can consult as well.

Garbage disposal discharging waste into the dishwasher

Now that we’ve described the process of plumbing a double kitchen sink with disposal and dishwasher; we’ll take a look at some of the most frequently encountered questions and problems that you might have regarding this setup.

And among these, the premier one is — what if you notice that your disposal waste is being backed up into your dishwasher?

This may happen because there’s a drain hose that represents a link between the disposal unit and the dishwasher. If there’s something clogged up in your garbage disposal, the water may start going in the opposite direction – thus ending up in your dishwasher.

Don’t worry, as you can prevent and deal with this issue easily. All you have to do is to pour some boiling water down the garbage disposal drain every week.

If there is any debris clogged up, this should wash it away. We recommend doing this even when you don’t notice a clog; such practices will prevent it from ever happening.

If you find that this hasn’t helped you — contact the nearest dependable plumber and ask them for assistance.

Frequently Asked Questions

Can you use the same circuit for the garbage disposal and the dishwasher?


Generally, you should know that both the dishwasher and the garbage disposal use 12/2 cables. Use a two-pole circuit breaker; one for the garbage disposal and one for the washer.

That way, if either of these needs to be fixed, you can turn them off easily for personal safety reasons.

Can you run the dishwasher while using your garbage disposal simultaneously?


Many people wonder if they can use their garbage disposal and their dishwasher at the same time. Remember, these two appliances share an identical drainage system of pipes. Thus, if you use them at the same time, you may find that you’ve got plumbing problems.

The best course of action would be to always make sure that there are no food waste particles remaining from the disposal before you use your dishwasher.

Can your garbage disposal affect your dishwasher?


Yes — especially if we’re talking about garbage disposal that you’ve just installed. You will find that there’s a rubber tube top that allows the dishwasher to drain into the same vent as the garbage disposal.

And newer garbage disposals contain a plastic plug; if you don’t pop this plug, the opening for the dishwasher will be closed.

Thus, you will have to do this or you will see the waste water from your dishwasher being unable to leave and being trapped in the appliance.

Is adding a double sink expensive?


The answer to this question depends on what you consider to be a good double sink. Naturally, you want to have a sink that looks great, but is also highly functional. Also, it needs to be compatible with appliances such as the dishwasher and garbage disposal.

Now, the prices on sinks vary; along with installation, this could set you back anything from $200 to $500. Of course, this is when we talk about standard models. There are always ridiculously expensive luxury sinks, but that’s probably not what you’re looking for.

How can I avoid clogging the garbage disposal?


We’ve already mentioned that you should take care not to clog up your garbage disposal; as this would also affect the inner workings of your dishwasher. For instance, you need to avoid clogging up by using hot water down the drain every once in a while.

Furthermore, you should also strive to avoid putting certain kinds of food in the garbage disposal. For instance, bones from meat, meat remains, and skin are all big no-nos. These will easily clog up your disposal; the same goes for oatmeal, pasta, and rice.

Once these foods harden, getting rid of them will be practically impossible. On this list, another surprising addition is eggshells; when grinded up, they can stick to parts of your disposal until you take it apart.

If you manage to make a habit out of avoiding all of this, you should have no trouble maintaining perfectly clean and functional garbage disposal.

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