Spill-resistant vacuum breaker (SVB)
A testable vacuum breaker that functions like a pressure vacuum breaker but is designed to avoid spilling water during pressurization, making it suitable for indoor use.
A spill-resistant vacuum breaker is a backsiphonage prevention assembly that works on the same principle as a pressure vacuum breaker: a spring-loaded check valve backed by an air inlet that opens when supply pressure is lost. The difference is in its internal design, which closes the air inlet before water reaches it during startup and pressurization. That refinement means the SVB does not spit or spill water in normal operation the way a standard PVB can.
The spill-resistant design matters most indoors. Laboratories, mechanical rooms, and commercial interiors often need vacuum breaker protection on equipment connections, but a device that discharges water onto a floor or bench during every pressurization cycle is unacceptable in those settings. The SVB fills that niche, providing testable backsiphonage protection under continuous pressure without the housekeeping problems. Like all vacuum breakers, however, it provides no protection against backpressure and must not be used where downstream pressure sources exist.
Testers and property owners should treat the SVB's siting rules like those of a PVB: it must be installed above the highest downstream outlet, remain accessible for testing and service, and be protected from freezing. Because it is a testable assembly with test cocks, it falls under the same periodic testing expectations as other assemblies, typically annual where required, set by the water authority. Confirm the application is strictly backsiphonage before accepting the installation.
Related terms
| Pressure vacuum breaker (PVB) | A testable backflow prevention assembly with a spring-loaded check valve and an air inlet valve that protects against backsiphonage only. |
| Atmospheric vacuum breaker (AVB) | A simple, non-testable backsiphonage prevention device that uses a float or disc to seal against flow and admit air when pressure is lost. |
| Backsiphonage | Backflow caused by a drop or loss of pressure in the supply piping that siphons water backward through a cross-connection. |
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