Air Gap

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Air Gap

What is Air Gap?

Air Gap: A vertical space that prevents back‑siphonage in plumbing, ensuring potable water safety.

Description

Air Gap is a commonly used term in the construction industry. An air gap is the unobstructed vertical distance between a water outlet (such as a faucet spout or discharge pipe) and the highest possible water level in the receiving vessel. By separating potable supply from contaminated water, the air gap eliminates back‑siphonage caused by negative pressure. Typical applications include dishwashers, water softeners, laboratory sinks, and irrigation systems. Codes mandate minimum air‑gap distances—usually twice the outlet diameter—for health protection.

FAQs

  • Why is an air gap necessary?

    It protects drinking water from contamination during backflow events.

  • Where are air gaps installed?

    At sink faucets, dishwasher drains, water softener discharges, and commercial food equipment.

  • How big should an air gap be?

    Typically, at least twice the outlet diameter or 1 inch, whichever is larger.

  • Is an air gap the same as a vacuum breaker?

    No vacuum breakers are mechanical; air gaps rely on open space.

  • Does plumbing code require air gaps?

    Yes—UPC and IPC mandate them for certain fixtures.

  • Can air gaps be concealed?

    They must remain open to the air; decorative covers are allowed if they are vented.

  • Who inspects air gaps?

    Plumbing inspectors verify compliance during rough-in and final inspections.

Fun Fact

Fun Fact: The concept of the air gap was formalized in U.S. plumbing codes after typhoid
Outbreaks linked to contaminated water in the early 1900s.

CSI Code

22 40 00

NAHB Code

2200