Winterizing a PVB in Colorado
Colorado winters make PVB maintenance non-negotiable. Because the device sits above ground and above the frost line, it’s exposed to freezing temperatures. Before the first hard freeze each fall — typically October in the Denver metro — the irrigation system should be blown out with compressed air and the PVB’s isolation valves should be shut off and the bonnet caps opened slightly to allow any remaining water to drain. A PVB that freezes with water trapped inside will crack its body or shatter the internal components, requiring full replacement. A split PVB can also go unnoticed until spring, when your irrigation system pressurizes and you discover water spraying from the device housing.
When a PVB Fails or Leaks
The most common sign of a failing PVB is dripping or spraying from the air inlet port on top of the device during normal irrigation operation. A small amount of dripping as the system pressurizes is normal; continuous discharge means the check valve or air inlet seal has worn and the device is no longer providing reliable backflow protection. Colorado water authorities can issue compliance notices or shut off service for failed or untested backflow devices, so don’t ignore a leaking PVB.
Done’s licensed plumbers handle PVB installation, testing, repair, and winterization throughout the Denver Front Range. Learn more on our pressure and backflow prevention page, or visit plumbing services for the full range of what we do. If you need help fast, our emergency plumbing team is available around the clock.
PVB vs. Other Backflow Preventers
Homeowners sometimes ask how a PVB differs from a reduced pressure zone (RPZ) device or a simple hose bib vacuum breaker. Here’s the quick comparison:
- Hose bib vacuum breaker: a small, inexpensive device threaded onto an outdoor spigot — protects only that connection, not a full irrigation system
- Pressure vacuum breaker (PVB): protects the entire irrigation system; must be above the highest outlet; not suitable for systems with continuous backpressure
- Reduced pressure zone (RPZ): offers the highest level of backflow protection; can be installed below grade; required when the risk of backpressure exists (e.g., booster pumps, chemical injection systems); typically required by water authorities for commercial or high-hazard residential applications
Winterizing a PVB in Colorado
Colorado winters make PVB maintenance non-negotiable. Because the device sits above ground and above the frost line, it’s exposed to freezing temperatures. Before the first hard freeze each fall — typically October in the Denver metro — the irrigation system should be blown out with compressed air and the PVB’s isolation valves should be shut off and the bonnet caps opened slightly to allow any remaining water to drain. A PVB that freezes with water trapped inside will crack its body or shatter the internal components, requiring full replacement. A split PVB can also go unnoticed until spring, when your irrigation system pressurizes and you discover water spraying from the device housing.
When a PVB Fails or Leaks
The most common sign of a failing PVB is dripping or spraying from the air inlet port on top of the device during normal irrigation operation. A small amount of dripping as the system pressurizes is normal; continuous discharge means the check valve or air inlet seal has worn and the device is no longer providing reliable backflow protection. Colorado water authorities can issue compliance notices or shut off service for failed or untested backflow devices, so don’t ignore a leaking PVB.
Done’s licensed plumbers handle PVB installation, testing, repair, and winterization throughout the Denver Front Range. Learn more on our pressure and backflow prevention page, or visit plumbing services for the full range of what we do. If you need help fast, our emergency plumbing team is available around the clock.
The Mechanics: What’s Actually Inside
Inside a PVB assembly you’ll find two key components: a check valve that only allows flow in one direction, and an air inlet valve (the vacuum breaker portion) that sits just above the check valve. Under normal operating pressure, the check valve stays open and the air inlet stays closed — water flows to your sprinklers unimpeded. When pressure drops on the supply side, a spring pushes the air inlet open, letting atmospheric air into the line. That air breaks any vacuum that would otherwise pull contaminated water back upstream. The whole cycle happens in a fraction of a second and is entirely automatic — no power required.
Where It Must Be Installed
A PVB must be installed at least 12 inches above the highest sprinkler head or outlet it serves, and it must be above grade — never buried or in a vault. This elevation requirement is critical: the device can only break a siphon if it’s physically higher than the potential contamination source. Colorado’s plumbing code and local water authority rules (including Denver Water and Aurora Water) require approved backflow prevention on any irrigation connection, and most require annual testing by a certified backflow technician.
PVB vs. Other Backflow Preventers
Homeowners sometimes ask how a PVB differs from a reduced pressure zone (RPZ) device or a simple hose bib vacuum breaker. Here’s the quick comparison:
- Hose bib vacuum breaker: a small, inexpensive device threaded onto an outdoor spigot — protects only that connection, not a full irrigation system
- Pressure vacuum breaker (PVB): protects the entire irrigation system; must be above the highest outlet; not suitable for systems with continuous backpressure
- Reduced pressure zone (RPZ): offers the highest level of backflow protection; can be installed below grade; required when the risk of backpressure exists (e.g., booster pumps, chemical injection systems); typically required by water authorities for commercial or high-hazard residential applications
Winterizing a PVB in Colorado
Colorado winters make PVB maintenance non-negotiable. Because the device sits above ground and above the frost line, it’s exposed to freezing temperatures. Before the first hard freeze each fall — typically October in the Denver metro — the irrigation system should be blown out with compressed air and the PVB’s isolation valves should be shut off and the bonnet caps opened slightly to allow any remaining water to drain. A PVB that freezes with water trapped inside will crack its body or shatter the internal components, requiring full replacement. A split PVB can also go unnoticed until spring, when your irrigation system pressurizes and you discover water spraying from the device housing.
When a PVB Fails or Leaks
The most common sign of a failing PVB is dripping or spraying from the air inlet port on top of the device during normal irrigation operation. A small amount of dripping as the system pressurizes is normal; continuous discharge means the check valve or air inlet seal has worn and the device is no longer providing reliable backflow protection. Colorado water authorities can issue compliance notices or shut off service for failed or untested backflow devices, so don’t ignore a leaking PVB.
Done’s licensed plumbers handle PVB installation, testing, repair, and winterization throughout the Denver Front Range. Learn more on our pressure and backflow prevention page, or visit plumbing services for the full range of what we do. If you need help fast, our emergency plumbing team is available around the clock.
A pressure vacuum breaker (PVB) is a backflow prevention device installed on irrigation and outdoor water lines to stop contaminated water from flowing backward into your home’s potable water supply. It works by using a spring-loaded check valve and an air inlet: when water pressure drops suddenly — as it does when a sprinkler system shuts off — the device opens to atmosphere, breaking the siphon before any dirty water (carrying fertilizer, pesticides, or soil bacteria) can reverse course and reach your drinking water. In Colorado, PVBs are among the most common backflow preventers on residential irrigation systems.
The Mechanics: What’s Actually Inside
Inside a PVB assembly you’ll find two key components: a check valve that only allows flow in one direction, and an air inlet valve (the vacuum breaker portion) that sits just above the check valve. Under normal operating pressure, the check valve stays open and the air inlet stays closed — water flows to your sprinklers unimpeded. When pressure drops on the supply side, a spring pushes the air inlet open, letting atmospheric air into the line. That air breaks any vacuum that would otherwise pull contaminated water back upstream. The whole cycle happens in a fraction of a second and is entirely automatic — no power required.
Where It Must Be Installed
A PVB must be installed at least 12 inches above the highest sprinkler head or outlet it serves, and it must be above grade — never buried or in a vault. This elevation requirement is critical: the device can only break a siphon if it’s physically higher than the potential contamination source. Colorado’s plumbing code and local water authority rules (including Denver Water and Aurora Water) require approved backflow prevention on any irrigation connection, and most require annual testing by a certified backflow technician.
PVB vs. Other Backflow Preventers
Homeowners sometimes ask how a PVB differs from a reduced pressure zone (RPZ) device or a simple hose bib vacuum breaker. Here’s the quick comparison:
- Hose bib vacuum breaker: a small, inexpensive device threaded onto an outdoor spigot — protects only that connection, not a full irrigation system
- Pressure vacuum breaker (PVB): protects the entire irrigation system; must be above the highest outlet; not suitable for systems with continuous backpressure
- Reduced pressure zone (RPZ): offers the highest level of backflow protection; can be installed below grade; required when the risk of backpressure exists (e.g., booster pumps, chemical injection systems); typically required by water authorities for commercial or high-hazard residential applications
Winterizing a PVB in Colorado
Colorado winters make PVB maintenance non-negotiable. Because the device sits above ground and above the frost line, it’s exposed to freezing temperatures. Before the first hard freeze each fall — typically October in the Denver metro — the irrigation system should be blown out with compressed air and the PVB’s isolation valves should be shut off and the bonnet caps opened slightly to allow any remaining water to drain. A PVB that freezes with water trapped inside will crack its body or shatter the internal components, requiring full replacement. A split PVB can also go unnoticed until spring, when your irrigation system pressurizes and you discover water spraying from the device housing.
When a PVB Fails or Leaks
The most common sign of a failing PVB is dripping or spraying from the air inlet port on top of the device during normal irrigation operation. A small amount of dripping as the system pressurizes is normal; continuous discharge means the check valve or air inlet seal has worn and the device is no longer providing reliable backflow protection. Colorado water authorities can issue compliance notices or shut off service for failed or untested backflow devices, so don’t ignore a leaking PVB.
Done’s licensed plumbers handle PVB installation, testing, repair, and winterization throughout the Denver Front Range. Learn more on our pressure and backflow prevention page, or visit plumbing services for the full range of what we do. If you need help fast, our emergency plumbing team is available around the clock.
