Capping off the Drain Hole when removing a Dishwasher

In most of the kitchens where a dishwasher and garbage disposal are used, the dishwasher is usually connected through a drain line with the garbage disposal. Drainage water from the dishwasher flows through this drainage line into the garbage disposal and then through plumbing, leaves the house. As long as the dishwasher is connected with the disposal, things go fine. The problem occurs when you have to remove the dishwasher. This leaves a hole in the top side of the garbage disposal where the dishwasher drainage pipe was connected before. In this article, I provide you the solution to this problem, and also you can read the Garbage Disposal Reviews to finding the best garbage disposal fo yourself.

Restaurant kitchen worker emptying a dishwasher removing clean cutlery from the basket in a close up on his hands Premium Photo

The Knockout plug: 

When a dishwasher is being connected to the garbage disposal, there is an important thing to do. Usually, there is a knockout plug covering the hole into which the dishwasher drainage pipe is fixed. When fixing the pipe, this knockout plug must be ‘knocked out’ to make sure that the dishwasher is drained successfully into the garbage disposal. 

Before installing a dishwasher, this knockout plug blocks the drain hole and so, there is no leakage from it. But when an installed dishwasher is removed, the knockout plug is not in place and the hole is left open on the side of the garbage disposal. From this hole, drainage water leaks and splashes creating a problem for you.  

How to plug this hole:

Plugging this hole is simple and you can do it yourself quite easily. All you need is a rubber cap and a clamp.

The rubber cap should be of 7/8” ID size. Usually, this size will fit in the drain hole. But to make sure, you can first measure your drain hole and then buy a rubber cap of that size. You can get such rubber caps from a hardware store or home supply store.

A clamp is needed to tightly hold the rubber cap in its place. You should buy a stainless worm gear clamp. They are available at a hardware store or home supply store. Some automotive supply stores also have these clamps but they call them radiator clamps.

If you can’t get these particular items, then you can use a rubber chair leg tip of compatible size. If you don’t already have one at home, then you can easily get them from home improvement stores. In place of worm drive clamps, you can use plumbing clamps that are also easily available at home improvement stores.

While removing your dishwasher, once you have plugged the drain hole with a rubber cap and tightened it with a clamp, you can be relieved of the worry of water leaking from the drain hole.


While removing the dishwasher and capping off the drain hole, the following precautions must be adopted.

  1. The circuit breaker to your kitchen must be switched off. Both the dishwasher and the garbage disposal are electrical devices having wires supplying current to them. Therefore, this should be the first thing you do.
  2. Turn off the water at the source and plug the drain hole in your sink and dishwasher. This is important because if water drains from the sink or dishwasher while you are removing the dishwasher or capping off the drain hole, it will come pouring out into the kitchen cabinet under your sink. As a result, your kitchen cabinet and floor may be flooded with water. This may cause irreparable damage to the woodwork in your kitchen.

This was a brief guide to plugging the drain hole when removing your dishwasher. I hope you find it helpful. But if you are still not able to completely resolve the problem, then you should contact a plumber.

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Christophe Rude

Christophe Rude

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