Dishwasher Drain Connection: How To Guide


There are two main types of dishwasher drain connections. These two types are the Air Gap and High Loop Method. With each of these two types of drain methods there are 2 ways to install each method so that they will work properly. 

Option 1: The Air Gap method: 

  1. Drain hose from air gap going directly into drain (above the p-trap) 
  2. Drain hose from air gap going directly into the garbage disposal 

Option 2: The High Loop Method: 

  1. Drain hose from high loop going directly into the drain (above the p-trap) 
  2. Drain hose from high loop going directly into the garbage disposal

 Before you decide which type of drain hose connection to install you need to check your states building code. Some states like California will require you to have an air gap. 

How to Find out Your Areas Dishwasher Drain Requirements

There are two very simple ways to find out if your area requires a specific type of drainage system.   

Solution 1: Google

All you have to do is google something similar to “(your state) dishwasher building code”. It should then take you to the states official website and explain what the requirements are. I will show you how to do this with an example using Minnesota.

Step one: enter your state and then dishwasher code

Step two: Click the relevant government page

Solution 2: Call a Local Plumber

Find local plumbers in your area using google. Call them up and ask them about the dishwasher drain requirements. These guys should be more then willing to answer any questions you might have about “codes”.

Installing a Dishwasher Air Gap

The purpose of the air gap filter is to make sure that when the dishwasher drains the dirty water will not back flow into the dishwasher. The dishwasher air gap is typically located on the sink right next to the tap. There is normally a cut out hole for the air gap to slide into.

What you will Need for Air Gap Installation

  • The air Gap
  • Two drain hoses
  • Four stainless steel hose clamps
  • Scissors or a knife
  • screw driver or a drill

Two Air Gap Set Ups

Air Gap Connected to the Drain Line

The first air gap set up is where the the drain hose is connected from the air gap directly into the drain. The key component to this set up is that the drain hose must be connected above the p-trap.

Air Gap Connected to the Garbage Disposal

The second air gap set up is when the drain hose is connected form the air gap directly into the garbage disposal.

Steps for Installing a Dishwasher Air Gap

Step 1: Place the Air Gap in the Correct Location

You are only temporarily placing the air gap in place so that you can measure out the hose distance properly.

Step 2: Measure and Cut the Drain Hose From the Dishwasher

Make sure that when you purchase your drain hoses that they are the correct size to attach the air gap. The air gap as you can see above has two places where you attach hoses which can require different sized drain hoses.

Place one end of the hose on the dishwashers drain outlet, then run the hose to the air gaps water inlet. Cut the hose to the appropriate length.

Step 3: Measure and Cut the Drain Hose From the Drain or Garbage Disposal

Place your other drain hose to the air gaps water outlet, then run it to either the drain connection (above the p-trap) or directly into the garbage disposal. Cut the hose to the appropriate length.

Step 4: Secure the First Hose

Secure the first hose to the dishwashers sump pump, and then to the air gap’s water inlet. If you purchased the correct size hose it should fit snug onto both places. However, you do not want a leak so you will use two stainless steel hose clamps to make sure no water will leak.

Step 5: Secure the Second Hose

Take your second measured out hose and connect it to the air gaps water outlet, and then to the correct place on your drain system. You will then want to secure this hose in place with two more stainless steel hose clamps on both connection points.

Step 6: Secure the Air Gap

With the drain hoses fully connected to the air gap you can now secure the air gap to the sink/counter. For this step you will take the cap off of the air gap and push it through the underside of the hole. There where be a nut/screw system that allows you to tighten the air gap in place. Place the cover back on the air gap and you are ready to go!

Installing a Dishwasher High Loop

The second most common type of dishwasher drain connection is the high loop method. The high loop method uses gravity to disallow the back flow of dirty water into the dishwasher. This works by pining the drain hose to the roof of the under side of the counter.

What you will Need for High Loop Installation

  • Drain hose
  • Two stainless steel clamps
  • Tape or a hook
  • Scissors or a knife
  • screw driver or a drill

Two Types of High Loop Set Ups

High Loop Connected to the Drain

In this set up the drain hose that is coming off of the bottom of the counter is hooked into drain line. Like I said above make sure that the drain hose is connected to the drain above the p-trap.

High Loop Connected to the Garbage Disposal

In this set up the drain hose is connected directly into the garbage disposal. Typically the inlet for the drain hose connection is located high up on the garbage disposal so that water drowns down into the garbage disposal chamber.

Steps for Installing a Dishwasher High Loop

Step 1: Locate the Area for the High Loop

The first thing that you need to do is find that area under the counter that you are going to secure the drain hose to. This area can be located anywhere in between the dishwasher and the sink or even behind the sink. You just want to make sure that no drain lines are coming down in front of the cabinet openings.

Step 2: Measure the Distance

For this step you will need to temporarily connect one end of the hose to dishwasher sump pump. Then place the hose to the location that you marked in step one and then place the hose to where it will connect to the drain or garbage disposal. Mark the place on the hose where it will connect to the drain/garbage disposal.

Step 3: Cut the Hose

After you have established the correct length of your high loop and you have marked it on the hose you will cut the hose. Use your scissors or a knife to cut the appropriate length.

Step 4: Connect Drain Hose to Dishwasher

Connect the one end of the hose to the dishwasher. Typically there will be a water outlet that is coming from the sump pump (this is where you attach the drain hose). Use a stainless steel hose clamp to tighten the hose onto the dishwasher.

Step 5: Secure Drain Hose to Counter

After you have connected to the drain hose to the dishwasher you need to secure the hose to the location on the counter that you chose in step 1. You can secure the hose using a hook that you screw into the bottom of the counter or a metal clamp you can also screw into the bottom of the counter.

Step 6: Connect Drain Hose to Drain or Garbage Disposal

Connect the other end of the drain hose to the drain above the p-trap or directly into the garbage disposal. Make sure that the hose does not droop before it enters the sink/garbage disposal or you will always have dirty water sitting int he hose (which can cause a nasty smell).

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