A properly functioning vacuum breaker should have little to no noticeable effect on your water pressure during normal use. These devices are designed to prevent backflow — not to restrict flow — so when they’re working correctly, you shouldn’t feel a difference at the spigot or hose bib. However, a vacuum breaker that is worn, clogged with mineral deposits, or incorrectly sized for your system can cause a measurable pressure drop. If you’ve recently had one installed and noticed lower pressure, a quick inspection is worth scheduling.

What a Vacuum Breaker Actually Does

A vacuum breaker is a type of backflow prevention device. Its job is to protect your potable water supply from contamination if a pressure drop or back-siphonage event occurs — for example, if the city main pressure drops suddenly while you have a garden hose submerged in a bucket of fertilizer. Without protection, that contaminated water could be drawn backward into your home’s pipes and eventually into the municipal supply.

The device works with a simple internal check mechanism: it allows water to flow forward normally, but if the pressure differential reverses, it opens an air vent to break the siphon rather than letting water flow backward. In Colorado, vacuum breakers are commonly required on outdoor hose bibs, irrigation systems, boiler fill lines, and certain commercial equipment connections.

When a Vacuum Breaker Can Affect Pressure

There are a few legitimate scenarios where a vacuum breaker does contribute to a pressure reduction:

  • Mineral scale buildup: Denver-area water is hard. Over time, calcium and magnesium deposits can build up inside the vacuum breaker body, narrowing the internal passages and restricting flow. This is the most common cause of pressure loss in aging devices.
  • Worn or stuck internal components: The rubber poppet or disc inside the device can degrade, swell, or stick in a partially closed position, which reduces flow even when it shouldn’t.
  • Incorrect sizing: A vacuum breaker that is undersized for the flow rate of its application will act as a bottleneck. This is most common on irrigation lines where a residential-grade device was installed on a higher-volume system.
  • Freeze damage: Colorado’s cold snaps — including hard freezes that can arrive well into spring at Front Range elevations — can crack vacuum breaker housings or damage the internal seal, causing partial blockages or constant dripping.

Atmospheric vs. Pressure-Type Vacuum Breakers

There are two main varieties you’ll encounter in residential settings. An atmospheric vacuum breaker (AVB) is the simpler of the two — it’s typically installed at individual hose bibs or irrigation valve stations and must be positioned at least six inches above the highest downstream outlet. A pressure vacuum breaker (PVB) is installed on the main irrigation supply line and can handle continuous pressure; it’s more common on full irrigation systems.

Pressure vacuum breakers are generally more robust and better suited to higher-flow applications, but they also have more internal components that can wear over time. If your irrigation system feels sluggish and you have a PVB on the supply line, that device deserves a closer look. Annual inspection is a reasonable maintenance step, particularly before each irrigation season starts in the spring.

How to Tell If Yours Is the Culprit

The simplest test is to check your pressure at multiple points. If pressure is low only at the outlet protected by the vacuum breaker — but normal elsewhere in the house — then the device is likely the issue. You can also listen for hissing or dripping from the air vent on the device when water is flowing; that’s a sign the internal seal is failing and the device needs service or replacement.

Do not remove the vacuum breaker to restore pressure. In Colorado, backflow prevention is required by code on outdoor hose connections and irrigation systems. Operating without it puts your household water supply at risk and can result in code violations.

What Done Can Do

The Done plumbing team tests, services, and replaces vacuum breakers and other backflow prevention devices across the Denver metro. If you’re unsure whether your device is functioning correctly — or if you’ve noticed unexplained pressure loss — we can diagnose the problem and get you back to full flow without compromising your water safety. Learn more on our pressure and backflow prevention page, or explore our full range of plumbing services for Front Range homeowners.