What Is an Air Gap in Plumbing? Understanding Its Importance for Backflow Prevention

Have you ever wondered what that little gap is between your kitchen faucet and the sink? It’s called an air gap, and it plays a crucial role in protecting your health and safety. In the plumbing world, an air gap is an unobstructed vertical space that prevents contaminated water from backing up into your clean water supply.

Air gaps are legally required by water health and safety regulations in many countries. They serve as the simplest form of backflow prevention, ensuring that any water that has already gone down the drain can’t flow back into your drinking water. Without proper air gaps, you could be at risk of consuming harmful bacteria, chemicals, or other contaminants.

What Is an Air Gap in Plumbing?

An air gap in plumbing is an unobstructed vertical space between a water outlet (like a faucet) and the flood level of a fixture (like a sink). It’s the simplest form of backflow prevention and is legally required in many countries for health and safety reasons.

How Air Gaps Work

Air gaps work by providing a physical separation between the end of a fixture’s drain and the receiving drain or vessel. This gap allows water to flow freely through the space, but if a backflow condition occurs, the air gap prevents contaminated water from reaching the fixture’s clean water supply.

For example, on a kitchen faucet, the air gap is the space between the end of the faucet and the top of the sink basin. Even if the sink were to clog and fill with dirty water to the rim, that water can’t reach the faucet outlet above it due to the air gap.

Air gaps rely on gravity to work, allowing waste water to flow down and away while stopping any backflow from reaching the clean water source above. When installed and maintained properly, air gaps provide a simple but highly effective layer of protection for your clean water. Reach out to us for affordable plumber services.

Types of Air Gap Devices

Several types of air gap devices are used in plumbing applications to prevent backflow and maintain the separation between clean water and wastewater. Let’s take a closer look at some common air gap devices:

Dishwasher Air Gaps

A dishwasher air gap is a fitting installed on the countertop or sink, typically near the kitchen faucet. It prevents contaminated water from the sink or garbage disposal from flowing back into the dishwasher. Here’s how it works:

1. The dishwasher drain hose connects to the air gap inlet.
2. The air gap outlet connects to the garbage disposal or sink drain.
3. When the dishwasher drains, wastewater flows up through the air gap and then down into the disposal or drain.
4. If a blockage occurs in the sink or disposal, the wastewater will overflow from the air gap, preventing it from entering the dishwasher.

Dishwasher air gaps are required by plumbing codes in many areas to ensure the sanitary operation of dishwashers.

Sink Air Gaps

Sink air gaps, also known as faucet air gaps, are similar to dishwasher air gaps but are designed for general sink use. They provide a physical separation between the faucet outlet and the sink’s flood level rim. Key points about sink air gaps include:

1. They are typically built into the base of the faucet.
2. Water from the faucet flows through the air gap and into the sink.
3. If the sink backs up, the wastewater cannot reach the faucet outlet due to the air gap.
4. Sink air gaps are especially important in situations where the faucet is used for filling containers or washing food.

Reverse Osmosis System Air Gaps

Reverse osmosis (RO) systems, which filter water for drinking and cooking, also utilize air gaps for backflow prevention. An RO system air gap works as follows:

1. The RO system’s drain water is routed upward to a small trough built into the base of the drinking water faucet.
2. The drain water then flows to the other side of the faucet stem and drops into a hole.
3. The water falls by gravity through a flexible tube to the drain.
4. The air gap ensures that no wastewater can be forced or siphoned back into the RO system from the drain.

RO system air gaps are crucial for maintaining the purity and safety of the drinking water produced by the filtration process.

By incorporating these air gap devices into plumbing systems, we can effectively prevent contamination and ensure the separation of clean water from wastewater in various applications throughout the home or workplace.

The Importance of Air Gaps in Protecting Drinking Water

Air gaps are crucial components in plumbing systems that safeguard our drinking water from contamination. By preventing backflow and siphonage, air gaps ensure that nonpotable water doesn’t mix with the clean water supply.

Preventing Backflow and Contamination

Air gaps protect potable water from the dangers of backflow and back siphonage. Backflow occurs when there’s a clog or blockage downstream in the drain line, causing contaminated water to back up and potentially reach the critical level (CL) of the air gap unit. Without an air gap, this nonpotable water could mix with drinking water, leading to serious health risks.

Back siphonage happens when there’s suction in the potable water line, which can draw contaminated water back into the clean water supply. Air gaps prevent this by maintaining a physical separation between the waste line and potable water line. This separation ensures that even if there’s suction or pressure changes, contaminated water can’t enter the drinking water system.

By incorporating air gaps in plumbing systems, we can significantly reduce the risk of cross-connections and keep our drinking water safe from harmful contaminants. Plumbing codes require air gaps for connecting waste lines of water treatment equipment to drain lines, highlighting their importance in protecting public health. Also read our how to guide for house plumbing to know what you need to do.

Air Gap Installation and Maintenance

Installing and maintaining an air gap is crucial for ensuring the proper functioning of your plumbing system and preventing contamination. Here’s what you need to know about air gap installation and maintenance.

Installing an Air Gap

Installing an air gap is a straightforward process that most homeowners can handle without the help of a plumber.

Cleaning and Maintaining an Air Gap

To keep your air gap functioning correctly and prevent leaks, regular cleaning and maintenance are essential.

By following these installation and maintenance tips, you can ensure your air gap provides reliable protection against contamination and backflow in your plumbing system.

Air Gap Codes and Requirements

Many plumbing codes across the United States require all dishwasher installations to include an air gap. Most codes stipulate that commercial food and beverage preparation sinks must have an air gap. Several states, including California, Washington, Minnesota, and Hawaii, have made dishwasher air gap installation mandatory for residential plumbing. In these states, a plumber installing a new dishwasher will require an air gap connection. If your system lacks an air gap, it won’t be up to code, and when selling your house, the inspector will require you to install one.

In the UK, legislation varies by country but includes the Water Supply (Water Quality) Regulations 2016 for England and the Water Supply (Water Quality) Regulations for Wales. European standards categorize and standardize the design and dimensions of air gaps appropriate for different uses:

• EN 13076: Unrestricted air gap (Family A, Type A)
• EN 13077: Air gap with non-circular overflow, unrestricted (Family A, Type B)
• EN 13078: Air gap with submerged feed incorporating air inlet plus overflow (Family A, Type C)

Additional standards cover each family and type of air gap, such as:

• Hydrostatic loop
• Pressure vacuum breaker
• Double check valve
• Chemigation valve
• Reduced pressure zone device
• Atmospheric vacuum breaker

These standards aim to prevent upstream contamination and ensure the proper installation and functioning of air gaps in various plumbing applications.

Air Gap Alternatives

If you live in an area where plumbing codes don’t mandate an air gap, there are other backflow prevention options available. Some homeowners dislike the pronounced appearance of air gaps on their counters and prefer to use alternative methods to separate wastewater from potable water.

High Loops

A high loop is a backflow prevention method where the dishwasher drain line runs to the highest point beneath the sink. I’ll affix the loop to the underside of the counter with a bracket, then it drains down into the garbage disposal or sink drain. In this setup, the drained water from my dishwasher is forced to travel upward before it can flow to the drain.

All high loops should measure at least 32″ above the kitchen floor. If there isn’t at least 32″ of clearance between the floor and the peak of the high loop, I’ll have to install an air gap. Since the tubing runs at a drastic slope, wastewater is unlikely to backflow through a properly installed high loop. This is known as an air break. If the drain becomes clogged, the waste should back up through the garbage disposal and into the sink rather than back into my dishwasher.

Standpipes

A standpipe is a vertical pipe above a P-trap that water drains into. P-traps are plumbing fixtures that prevent sewage and odors from wafting from the drain back into my home. Standpipes must be vented and at least 2″ in diameter. They’re most often used to rapidly drain washing machines between fill and drain cycles, but some homeowners install standpipes under the sink to circumvent installing an air gap.

Generally, it’s unwise to install a standpipe beneath my sink for a dishwasher. It’s overly complicated and less effective than both air gaps and high loops. Standpipes must be taller than the sink’s flood level, or else water can overflow into my cabinet. Unlike air gaps and high loops, they also require excessive plumbing work. In most instances, it’s unlikely that a plumber would ever recommend a dishwasher standpipe as the ideal solution for draining my dishwasher.

Conclusion

Air gaps play a crucial role in protecting my home’s water supply from contamination. By providing a physical separation between the water outlet and the flood level of a fixture, they prevent harmful backflow and back siphonage.

I’ve learned that air gaps are not only important for my health and safety but are also required by many plumbing codes. They’re essential for various applications, including dishwashers, ice makers, and water softeners.

While alternatives like high loops exist, air gaps remain the most effective and reliable method for backflow prevention. By understanding their function, installation, and maintenance, I can ensure my plumbing system is properly protected.

Incorporating air gaps into my home’s plumbing is a simple yet powerful way to safeguard my family’s well-being and maintain a clean, contaminant-free water supply.

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