Air gap (plumbing)


Air gap (plumbing)

An air gap, as it relates to the plumbing trade, is the unobstructed vertical space between the water outlet and the flood level of a fixture.

A simple example is the space between a wall mounted faucet and the sink rim (this space is the air gap). Water can easily flow from the faucet into the sink, but there is no way that water can flow from the sink into the faucet without modifying the system. This arrangement will prevent any contaminants in the sink from flowing into the potable water system by siphonage and is the least expensive form of backflow prevention.

To further illustrate the air gap, consider what could happen if the air gap were eliminated by attaching a hose to the faucet and lowering the hose into a sink full of contaminated water. Under the right conditions (if the water supply loses pressure and the sink is higher than the point at which the water supply enters the house, for instance), the dirty water in the sink will be siphoned into the water pipes through the hose and faucet. The dirty water then will be dispersed throughout the drinking water system.

All plumbing codes require backflow prevention in several ways. The plumbing fixture manufacturers build the fixtures to meet these codes. A plumber must not build cross-connections in his daily work practices, and Plumbing Inspectors look for improper designs or connections of piping and plumbing fixtures.

An air gap must meet the requirements of being two times the inner diameter of the pipe (2*D) in order to be sufficient. However, an air gap MUST NOT be less than one inch, and NEED NOT be more than twelve inches. Air gap is measured from the end of the faucet to the upper rim of the reservoir (sink, drain, etc.).

See also

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


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Air gap — may refer to: * Air gap used in transformers to limit short circuit current. * Air gap (computing) in computer networks to isolate sections physically. * Air gap (plumbing) in context of plumbing. * Air gap was the area not covered by American,… …   Wikipedia

  • air gap — noun 1. : an air filled gap in a magnetic or electric circuit (as the space between the field magnet poles and the armature in a dynamo or motor) 2. : wind gap 3. : the vertical distance between the point where water enters a plumbing fixture (as …   Useful english dictionary

  • Tap water — Indoor Tap commonly found in the bathroom or kitchen. This tap is a single handle, double spout tap (one spout for hot water, one spout for cold water). Tap water (running water, city water, municipal water, etc.) is a principal component of… …   Wikipedia

  • Backflow prevention device — See also: Backflow (plumbing) In this situation, dirty water from the hillside pool will back siphon or back flow down the hosepipe and into the clean water tank. To prevent this from happening, the house s external tap should be fitted with a… …   Wikipedia

  • Siphon — Not to be confused with Psiphon. This article is about the domestic device. For the animal organ, see siphon (disambiguation). Siphon principle …   Wikipedia

  • Termite pre-treatment — What are Termite Pre Treatments? Pre treatment is a term for poison that is applied to the soil. This page relates principally to the Continental USA as other parts of the world (including Hawaii) often have less toxic approaches to termite… …   Wikipedia

  • Hydrostatic loop — A hydrostatic loop, though not often used in plumbing practice, is an arrangement of pipes formed into a vertical loop to prevent backflow of water within the plumbing potable water system. Since a siphon has a maximum height that it can work… …   Wikipedia

  • Building insulation — refers broadly to any object in a building used as insulation for any purpose. Whilst the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation. Often an… …   Wikipedia

  • Pressure — This article is about pressure in the physical sciences. For other uses, see Pressure (disambiguation). Pressure as exerted by particle collisions inside a closed container …   Wikipedia

  • Atmospheric vacuum breaker — An Atmospheric Vacuum Breaker (AVB) is a backflow prevention device used in plumbing to prevent backflow of non potable liquids into the drinking water system. It is usually constructed of brass and resembles a 90 degree elbow with a hood on its… …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.