The spill-resistant vacuum breaker (SVB) prevents cross-connections without allowing a water spill. The 4W-500 Series valve is designed to prevent contamination of the potable water supply due to back-siphonage. The SVB is ideally suited for continuous pressure, indoor applications, where water spillage is undesirable. During normal flow conditions, the SVB's check valve remains open. The atmospheric vent seals in the bonnet assembly. As the line pressure falls to 1 psi, the spring loaded atmospheric vent opens and the check valve closes, breaking the vacuum and thereby preventing back-siphonage. Water is prevented from spilling during operation. Conbraco Industries, Inc. P.O. Box 247 Matthews, NC, 28106