What is an Atmospheric Vacuum Breaker (AVB) and Why Do You Need One?

Have you ever wondered how your clean drinking water stays safe from contaminants potentially lurking in your garden hose or irrigation system? One key, often unseen, hero in this battle is the Atmospheric Vacuum Breaker, or AVB.

But what exactly is it, and why is it so important?

Understanding the Threat: Backsiphonage

Imagine water flowing backward from a potentially contaminated source (like a puddle your hose is sitting in, or a sprinkler head) into your home's clean water supply. This dangerous phenomenon is called backsiphonage, a type of backflow.

It occurs when there's a sudden drop in pressure in the main water supply line (like during a water main break or heavy usage nearby), creating a vacuum that can suck non-potable water back into your pipes.

Enter the Atmospheric Vacuum Breaker (AVB)

An AVB is a simple yet ingenious mechanical backflow prevention device. Its primary job is to stop backsiphonage before it can happen. It's designed specifically for plumbing connections where contaminated water could potentially be drawn back into the clean water system.

How Does an AVB Work?

The magic of an AVB lies in its air inlet valve (or poppet).

1. Normal Operation: When water flows normally through the AVB towards its outlet (like a sprinkler head), the water pressure keeps the air inlet valve closed.

2. Pressure Drop (Vacuum Condition): If the pressure in the supply line drops significantly, creating a potential vacuum, the internal check valve closes. Simultaneously, the air inlet valve opens, allowing atmospheric air to enter the downstream side of the device.

3. Breaking the Siphon: This influx of air breaks the vacuum (siphon effect), preventing any potentially contaminated water from being pulled backward past the AVB and into your potable water lines.

Where Are AVBs Used?

AVBs are commonly found in specific applications:

• Irrigation Systems: Often installed on lawn sprinkler zones to prevent fertilizers, pesticides, or dirty sprinkler water from contaminating the main water supply.

• Hose Bibbs (Outdoor Faucets): Many modern hose bibbs have built-in AVBs or require one to be attached.

• Utility Sinks and Service Faucets: Used where hoses might be attached and submerged in potentially non-potable water.

Important Considerations

AVBs must be installed vertically, at least 6 inches above the highest downstream outlet (e.g., the tallest sprinkler head), and cannot be subjected to continuous water pressure for more than 12 hours.

They are not suitable for applications with backpressure.Protecting your potable water is crucial for health and safety. The humble Atmospheric Vacuum Breaker (AVB) plays a vital role in this protection, preventing dangerous backsiphonage and ensuring your drinking water remains uncontaminated. Check your irrigation systems and hose bibbs – you likely rely on an AVB every day!