Air Gap
The Air Gap is a non-mechanical piping arrangement backflow prevention method with no moving parts. The Air Gap is a very effective technique to prevent both backsiphonage and backpressure. The Air Gap should be used whenever practical since it is the best method of preventing backflow. This piping arrangement is permanently fixed and has been used for many years by the plumbing industry to prevent the interconnection between potable water system and the waste disposal system. The air gap must be twice the supply pipe diameter but never less than one inch above the flood level rim. Air gaps are not exempt from an in- depth cross-connection control program requiring periodic inspection of all backflow methods and should be inspected as frequently as mechanical backflow prevention devices/assemblies.
When contemplating the use of an air gap, some other considerations are:
- In a continuous piping system, each air gap requires the added expense of reservoirs and secondary pumping systems.
- Excessive splash may be encountered in the event that higher than anticipated pressures or flows occur. The splash may be a cosmetic or true potential hazard.
Air gaps in plumbing fixtures and appliances such as but not limited to faucets sinks, dishwashers, and washing machines shall comply with the American Society of Mechanical Engineers (ASME) Standard A112.1.3 Air Gaps in Plumbing Systems (For Plumbing Fixtures and Water-Connected Receptors).
The air gap method is fashioned at end of the water service line service where reservoirs or storage tanks are in use.
An air gap, although an extremely effective backflow prevention method to prevent backsiphonage and backpressure conditions, interrupts the water flow resulting in a loss of pressure downstream of the air gap. In order to maintain pressure downstream of the air gap pumps must be utilized.
Air gaps may be fabricated from commercially available plumbing components or purchased as separate units and integrated into plumbing and piping systems.
