Backflow Preventer
CSI Division 22, Plumbing
A plumbing device installed on a water supply line specifically to stop contaminated water from flowing backward into a building's or municipality's clean drinking water supply, required at any connection point where a cross-connection to a non-potable source (an irrigation system, a fire sprinkler system, a boiler) creates a realistic risk of backflow.
Why it matters
Backflow preventers are one of the few plumbing devices that require regular, code-mandated testing by a certified tester after installation, not just at initial inspection, precisely because a device that fails silently could allow contamination into a drinking water system without anyone noticing until people are already affected.
On a real project
A building's irrigation system, which draws from the same water supply as the drinking water system, includes a backflow preventer at the connection point, certified and tested annually to confirm it's still functioning to prevent contaminated irrigation water from siphoning back into the potable water supply.
Who this matters most to
A Plumber installs backflow preventers at every required cross-connection point per code and the local water authority's requirements. A Quality Control Manager confirms the required initial certification testing is completed and documented before the system is accepted.
Where this goes wrong
A project installs an irrigation system tied into the building's potable water supply without a required backflow preventer, treating it as a minor detail since the irrigation system itself doesn't seem hazardous. A local water authority inspection catches the missing device, and the project has to add it after the fact, a straightforward fix, but one that should have been caught in the original plumbing design and permit review.