📖 8 Minute Read
A backflow preventer is a mechanical plumbing safety device designed to stop contaminated water from flowing backward into a clean drinking water supply. When changes in water pressure occur, untreated or contaminated water can reverse direction and enter the potable water system.
A properly installed and maintained backflow preventer automatically prevents this reverse flow, helping protect people, buildings, and the municipal water supply.
By the end of this guide you'll understand:
✅ What is backflow
✅ Why backflow prevention is important
✅ How a backflow preventer work
✅ Common types of backflow preventers
✅ Where backflow preventers are used
✅ If backflow preventers require annual testing
✅ Common signs of problems
✅ Whether you should repair or replace, if failed
Backflow is the unwanted reversal of water flow within a plumbing system. It occurs when pressure conditions change and contaminated water is pulled or pushed into the clean drinking water supply. Backflow can result from backsiphonage or backpressure and may introduce chemicals, bacteria, fertilizers, stagnant water, or process fluids into potable water.
Protecting drinking water is the primary purpose of backflow prevention. Municipal Cross Connection Control Programs require many properties to install and maintain approved backflow prevention assemblies because contamination can affect not only a single building but also portions of the public water distribution system.
Inside most backflow prevention assemblies are spring-loaded check valves. During normal operation, water flows through the assembly without restriction. If reverse flow begins, the check valves close automatically. Reduced Pressure Principle Assemblies also include a relief valve that provides additional protection for high-hazard applications.
Reduced Pressure Principle Assembly (RP): High hazard protection.
Double Check Valve Assembly (DCVA): Low hazard protection.
Pressure Vacuum Breaker (PVB): Commonly used on irrigation systems.
They are commonly installed in commercial office buildings, restaurants, warehouses, industrial facilities, schools, healthcare facilities, hotels, agricultural properties, irrigation systems, fire protection systems, retail centres, and strata developments.
Most testable backflow prevention assemblies require annual certified testing. A certified tester uses calibrated differential pressure gauges to verify the assembly continues operating correctly. Test results are submitted to the municipality where required.
Visible leaks, water discharge from a relief valve, corrosion, physical damage, low water pressure, or a failed annual test may indicate that the assembly requires repair or replacement.
Many failed assemblies can be repaired using manufacturer-approved parts. Replacement is generally recommended only when the device is beyond economical repair, obsolete, or no longer meets code requirements.
📌 Annual Backflow Testing Guide
📌 Backflow Preventer Repair Guide
📌 Backflow Preventer Installation Guide
📌 Backflow Testing Cost Guide
📌 Cross Connection Control Explained
