What is air gap plumbing, and why do we need it

Sometimes, a simple mechanism can help prevent serious health hazards. Take air gap plumbing for example. It’s one of the most straightforward approaches to preventing backflow.  

In plumbing systems, the separation of potable water and wastewater through distinct pipes is essential to prevent contamination. However, despite this intentional design, the risk of backflow always exists, allowing wastewater to mistakenly enter the freshwater supply line. An air gap acts as a barrier, preventing the mixing of potable and non-potable water. This is the reason the simple yet effective design is commonly integrated into various home plumbing fixtures.

What is an air gap plumbing?

In plumbing, an air gap works like a safety space (usually at least one inch big) between a pipe or faucet and the top of a sink. It’s there to keep the water supply away from any potentially dirty water in the sink. This gap is something that plumbing codes require, especially for home appliances such as dishwashers, to stop contaminated water from going back into the clean water supply. Think of it as a safety measure to make sure yucky stuff doesn’t sneak back into our drinking water. 

It’s crucial because without it when water systems are turned off or if plumbing isn’t done right, dirty water could flow back and cause serious health problems. Keep in mind that the plumbing code is there to keep us all safe from these kinds of risks.

Some of the common appliances and fixtures that require air gap plumbing include dishwashers, Reverse Osmosis (RO) systems, water softeners, sinks, commercial ice makers, and food-handling equipment. 

How does air gap plumbing work?

An air gap is a good way to keep clean water safe from contamination. When clean water comes out of a fixture, like a faucet, it either gets used or goes down the drain. We never want the stuff in the drain, especially if there’s a backup or flood, to mix with our clean water. Both plumbing systems, one for clean water and one for waste, should always stay separate. If they accidentally mix (called a “cross-connection”), it can seriously mess up the clean water supply. This can happen in a backflow event, where stuff from the dishwasher drain line gets pulled into the clean water supply due to siphoning or pressure differences.

Air gaps solve this problem by creating a gap of air that water and waste have to cross before reaching the clean water supply. This gap is between the outlet of a fixture (like a faucet) and the highest point of a receptacle (like a sink or floor drain). Imagine water flowing from a faucet to a sink. Even if the sink backs up, drain water can’t reach the faucet because of the space.

The faucet and sink example is a good way to understand the term air gap. Dishwasher air gaps are common, but there are other situations where a direct drain connection is not allowed, and an air gap is needed.

How to put in a dishwasher air gap? 

Having an air gap installed could be a DIY job that you can handle without calling in a plumber. Here’s a step-by-step guide:

Find the air gap hole

• Look for the air gap hole on your counter. If it’s not there, you might see a flat disc-shaped cover. Take it off.
• If there’s no hole, you’ll need to make one. Use an electric drill and hole saw to create a 1-3/8” hole close to your sink rim, but be careful not to flood your counter.
• If it’s granite or marble, think about getting a licensed pro to help.

Connect to the dishwasher drain hose

• The dishwasher drain hose goes to the smaller leg of the air gap.
• Attach a 5/8″ tube to the 5/8″ leg of the air gap.
• Use stainless steel hose clamps to secure it tightly.

Connect to drain hose or garbage disposal

• Cut a 7/8“ tube to connect the air gap to your drain or garbage disposal. Secure it with a hose clamp.
• If it’s going to the drain, connect it to the Y-branch tailpiece with another hose clamp. Make sure your Y-branch is good for 7/8″ tubing.
• If it’s going to a garbage disposal, remove the metal plug from the disposal’s tube and attach the 7/8″ tubing with a hose clamp.

Put the air gap through the counter

• Take off the vanity covering on the air gap and push it through the hole in the counter from below.
• Tighten it against the counter by twisting the nut along the air gap’s threads. Use a wrench to make it super secure.
• Put the vanity cover back on.

Check for leaks

• Run your dishwasher on a full cycle.
• Keep an eye on the air gap and tubing for any signs of leaking. Make sure no water is escaping and causing trouble in your cabinet.

What is the advantage of installing an air gap?

Though a small part of the plumbing system, air gaps can really make a difference in preventing contamination and enhancing safety. 

• An air gap prevents backflow by acting as a barrier. It stops dirty water from flowing back into the clean water supply.
• Ensures code compliance. Many plumbing codes mandate the use of air gaps, especially for appliances such as dishwashers.
• Acts as a safety measure by preventing the risk of wastewater siphoning back into the drinking water supply. This is particularly dangerous during events such as city main shutdowns or when plumbing is improperly done, which can pose potential health risks.
• Reduces the chance of contamination from various sources, such as hoses in mud puddles or contact with harmful substances such as bleach water. This helps prevent incidents that could lead to severe consequences, including loss of life.
• Is a proactive step to safeguard public health by minimizing the possibility of waterborne diseases or other health hazards associated with contaminated water.

Read more: Which plumbing work doesn’t require a license

Written by Ramona Sinha. April 20, 2024

Ramona is the Senior Content Writer for Kukun. This experienced blogger uses simple and succinct words to decipher the complex phenomenon called life. She has written articles covering a broad range of topics, such as real estate, lending and mortgage, finance, business, taxation, home designs, home improvement projects, decor concepts, and more. An avid traveler, she’s a digital nomad at heart and an animal lover from the depth of her soul.