§890.TABLE C. Minimum Air Gaps for Plumbing Fixtures

	Minimum Air Gap (Inches)
	When Not Affected by Near Wall1	When Affected by Near Wall2
Lavoratories and other fixtures with effective opening not greater than ½ inch diameter.	1	1½
Drinking water fountains, single orifice not greater than 7/16 (0.437) inch diameter or multiple orifices having total area of 0.150 square inches (area of circle 7/16 inch diameter).	1	1½
Sink, laundry trays, goose neck bath faucets and other fixtures with effective opening not greater than one inch diameter.	1½	2¼
Stills, sterilizers and other appliances, fixtures, devices and water and waste connections used for preparation of sterile material.	2	3
Over rim bath fillers and other fixtures with effective openings not greater than one inch diameter.	2	3
Effective openings greater than one inch.	2 X Diameter of effective opening	3 X Diameter of effective opening
1   Side walls, ribs or other similar obstructions do not affect air gaps when spaced from inside edge of spout opening a distance greater than three times the diameter of the effective opening for a single wall, or a distance greater than four times the diameter of the effective opening for two intersecting walls.
2   Vertical walls, ribs or similar obstructions extending from the water surface or to above the horizontal plane of the spout opening require a greater air gap when spaced closer to the nearest inside edge of spout opening than specified in Footnote 1 above. The effect of three or more such vertical walls or ribs has not been determined. In such cases, the air gap shall be measured from the top of the wall.