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How To Cap Off Dishwasher Drain On Garbage Disposal

All garbage disposals come with a dishwasher inlet which is basically a small 7/8 inch size (outer diameter) pipe extension. The outlet hose from the dishwasher is connected to this extension, so the food debris coming through it passes through the garbage disposal. But how to cap off this dishwasher drain hole once you decide to remove the dishwasher?

The dishwasher drain on a garbage disposal can be capped off using a simple conical rubber plug that is 3/4 inches wide on its wider side. Simply push the rubber plug into the drain hole to cap it. You can also gently tap it with a hammer to make it tighter.

You can buy this plug from here on Amazon.

Lamprey Hardware #1-5 Universal Rubber Winter Plug for 1/2 inch to 1 inch Holes - Tapered Variety Multipurpose LHTP15 (1)

Capping off the drain with a rubber plug

Here is how to cap off the drain connection using the above conical rubber plug;

  1. Turn off the garbage disposal and the dishwasher. Make sure that both the plumbing appliances are fully drained.
  2. Put a bucket under the sink and disconnect the dishwasher connection. The dishwasher hose is secured using a clamp. Loosen this clamp using a screwdriver or a plier. Once the clamp is loose, twist the hose back and forth to easily remove it.
  3. Take the rubber plug, which you can buy from HomeDepot or any local hardware store, and push it into the dishwasher inlet of the garbage disposal with the smaller face in. Push the plug fully into the drain hole. Use the side face of a hammer if necessary.
  4. Run the garbage disposal with plenty of water and check for leaks.

Below is a video tutorial of this process;

How to cap off the dishwasher drain on garbage disposal

Capping off the inlet with a dishwasher connector kit and a copper cap

The easiest way to cap off a disposal’s dishwasher inlet is by using a rubber plug, as mentioned above. An alternate method is using a dishwasher connector kit and a 1/2 inch copper cap.

Here is how to do it;

  1. Remove the dishwasher hose from the garbage disposal by loosening its clamp. Make sure to keep a bucket under it to catch any water left in the hose.
  2. Cut the dishwasher connector to the appropriate size. Push the copper cap into the connector and secure it with the clamp that comes with the kit
  3. Connect the other end of the connector to the dishwasher inlet of the garbage disposal. Tighten the connection with a clamp.

Below is a video demonstrating this process;

The kit and the copper cap cost around $20, so this is definitely an expensive method compared to capping off the drain with a rubber plug.

What is the purpose of the dishwasher inlet?

The purpose of the dishwasher inlet on a garbage disposal is to connect the dishwasher outlet hose to the garbage disposal. This is done to drain the dishwasher through the garbage disposal instead of draining it directly into the drain pipes.

dishwasher inlet on a garbage disposal
dishwasher inlet on a garbage disposal

There are two reasons for doing this; here are they;

  1. When a dishwasher is directly connected to the drainpipe, any backup water will flood the dishwasher and the kitchen cabinet as there is no other way for the water to go. But if the dishwasher drains through the garbage disposal, the backup water will fill the sink since the garbage disposal opens up into the sink. So connecting your dishwasher to the garbage disposal prevents many messy floods in the kitchen and the tedious cleaning after it.
  2. The wastewater from the dishwasher has food particles in it. When the dishwasher drains through the garbage disposal, the garbage disposal will catch large food particles, if any, which are later ground and disposed of. But when the dishwasher directly drains into the drain pipes, these food wastes can cause clogs.

The size of this garbage disposal dishwasher drain is 7/8 inches in outer diameter. You can use a dishwasher connector kit to connect hoses of varying sizes to it.

How to remove the knockout plug from a garbage disposal?

As I mentioned before, all garbage disposal models come with a dishwasher inlet. This inlet is capped off by a knockout plug that is made of plastic. If you are going to connect a dishwasher to it, you have to first remove this plug. Removing this is easy;

  1. Locate the dishwasher inlet. It is on the same side as the disposal outlet.
  2. Insert a screwdriver into the inlet hole and gently tap it with a hammer. Do not knock it hard, as this will pierce the plug instead of knocking it out.
  3. The knockout plug will land inside the garbage disposal. Look for it using a flashlight and remove it using a needle nose plier.

Some Moen garbage disposal models come with a dishwasher plug that can be twisted off using a screwdriver. You can reuse this plug to close the inlet if you decide to disconnect the dishwasher and the garbage disposal.

You should remove this knockout plug before mounting the garbage disposal to the sink. Once the garbage disposal is installed, it is difficult to remove this plug, especially if there isn’t much space under the kitchen sink.

Sometimes people forget to remove the knockout plug before hooking up the dishwasher with the garbage disposal. As a result, the dishwasher will not drain, and the water will back up, flooding the kitchen. So it is important that you remove this plug correctly before connecting to a dishwasher.

Cons of connecting dishwasher and garbage disposal

Dishwashers are connected to garbage disposals in most houses. But it is also possible to connect a dishwasher directly to the drain pipes. Connecting your garbage disposal and dishwasher can cause water to back up into the dishwasher if the garbage disposal is not properly installed. Improper installation of a garbage disposal will clog the pipes immediately to it, which will also affect the proper working of your dishwasher. If your garbage disposal is prone to clogs, it is better to drain the dishwasher separately.

My name is Thomas Anderson, author of DisposalQA. I have 15 years experience working as a plumber in CA, and this is where I answer common questions about garbage disposals.