Editing Backflow prevention device (section)

==Preventive devices==
[[File:Verifiedbackflow.jpeg|thumb|Backflow prevention device]]
The simplest, most reliable way to provide backflow prevention is to provide an [[air gap (plumbing)|air gap]]. An air gap is simply an open vertical space between any device that connects to a plumbing system (like a valve or faucet) and any place where contaminated water can collect or pool. A simple air gap has no moving parts, other than flowing water. Many [[plumbing code]]s specify a minimum air gap distance required for various circumstances, such as a drain connection for a dishwasher, e.g., [[BS 6282]].

Alternatively, a specialized backflow preventer valve may be installed at strategic locations in the plumbing system wherever there is a risk of contaminated fluids entering the water supply pipes. These valves are used where there is not sufficient vertical clearance or physical space to install an air gap, or when pressurized operation or other factors rule out use of an air gap. Because these valves use moving parts, they are often required to be inspected or tested periodically.