What is a backflow device & How are they tested?

What is a Backflow Preventer?

A backflow preventer is a specialized device designed to stop contaminated water from flowing backward into clean water supplies. These devices are crucial in preventing pollutants, chemicals, or bacteria from entering drinking water systems due to changes in pressure. Backflow can occur in commercial, industrial, and residential properties, making prevention essential for public health and safety.

How Are Backflow Preventers Tested?

Backflow preventers must be tested annually to ensure they are functioning correctly. A certified backflow tester follows these steps:

1. Turn Off Water Supply: The tester temporarily shuts off the water to prevent interference during testing.
2. Connect Test Equipment: A differential pressure gauge is used to measure the internal components' function.
3. Check for Proper Operation: The tester evaluates the check valves, relief valves, and air gaps to confirm they are preventing backflow effectively.

Record & Submit Results: If the device passes, the results are submitted to the local water authority. If it fails, repairs or replacement are required before retesting. Regular testing ensures compliance with local regulations and protects public water supplies from contamination. Property owners should schedule their annual backflow test with a certified professional to stay compliant and maintain water safety.

Common Types of Backflow Preventers:

Reduced Pressure Principle Backflow Preventer (RPZ)

Reduced Pressure Principle Backflow Preventers (RPZ or RPBP) are commonly connected to systems where backflow could introduce contaminants into the potable water supply. These typically include:

1. Irrigation Systems – Protects against fertilizers, pesticides, and other chemicals from siphoning back into the potable water supply.
2. Fire Protection Systems – Prevents stagnant or chemically-treated water in fire sprinkler systems from contaminating drinking water.
3. Boiler Systems – Stops chemically-treated water in boilers from flowing back into the main water supply.
4. Industrial Facilities – Used where hazardous chemicals or processes could contaminate potable water.
5. Medical & Laboratory Facilities – Protects against biological and chemical contaminants.
6. Commercial & Restaurant Equipment – Used in systems like soda dispensers (with carbonated water) to prevent backflow from CO₂ pressure changes.
7. Cooling Towers – Prevents water with biological growth inhibitors or other chemicals from re-entering the potable water system.

These are required in high-hazard situations where backflow could introduce pollutants or contaminants harmful to health.

Double Check Valve Backflow Preventer (DC)

Double Check Valve Backflow Preventers (DCs) are commonly connected to systems where there is a moderate hazardof backflow contamination. They are used when pollutants (not toxic substances) could enter the potable water supply. Common applications include:

1. Fire Sprinkler Systems – Protects against stagnant water but is used when chemicals (like antifreeze or foam) are not added to the system.
2. Irrigation Systems (Non-Chemical) – Used in sprinkler systems that do not inject fertilizers, pesticides, or chemicals.
3. Commercial Water Services – Installed in businesses that require moderate backflow protection but don’t handle hazardous substances.
4. HVAC Systems (Closed-Loop) – Used in heating and cooling systems where backflow might introduce non-toxic materials like scale inhibitors.
5. Swimming Pools (Filling Systems) – Prevents pool water from siphoning back into the drinking supply when filling, as long as no chemicals are injected into the fill line.
6. Food Processing Facilities – Applied where potable water is used in processing but without hazardous contaminants.
7. Apartment & Commercial Buildings – Protects water supplies from cross-connections in multi-unit properties.

DC backflow preventers are often chosen when the risk is pollution (affecting taste, color, or odor) rather than contamination (posing health hazards). If a higher-risk substance is present, an RPZ (Reduced Pressure Zone) device is typically required instead.

Pressure Vacuum Breaker Backflow Preventer (PVB)

Pressure Vacuum Breaker (PVB) Backflow Preventers are commonly connected to systems where there is a risk of back-siphonage but not backpressure. They are typically used in low to moderate hazard applications where contaminants could enter the potable water supply due to siphoning. Common applications include:

1. Irrigation Systems – The most common use, preventing fertilizers, pesticides, and stagnant water from siphoning back into the drinking water supply.
2. Garden Hose Connections – Sometimes used on outdoor hose bibs to prevent contaminated water from being drawn back into the home’s plumbing.
3. Fountains & Decorative Water Features – Used when potable water is supplied to ornamental ponds or fountains.
4. Hydroponic Systems – Prevents nutrient-rich water from contaminating the potable water source.
5. Car Wash Systems – Protects against back-siphonage of soaps, detergents, or rinse water in certain setups.

Important Considerations:

✔️ PVBs must be installed above the highest downstream outlet (usually 12 inches above the highest sprinkler head in irrigation systems).

✔️ They are not suitable for systems with continuous pressure (e.g., main water supply lines).

✔️Only protects against back-siphonage, not backpressure, making them inappropriate for applications where pressure from downstream could push contaminants back into the potable supply.

✔️ If both back-siphonage and backpressure protection are needed, an RPZ or DCVA (Double Check Valve Assembly)is typically required instead.

Spill-Resistant Vacuum Breaker Backflow Preventer (SVB)

Spill-Resistant Vacuum Breaker (SVB) Backflow Preventers are commonly connected to systems where there is a risk of back-siphonage (but not backpressure), similar to a Pressure Vacuum Breaker (PVB), but with the added advantage of being designed to prevent water spillage upon activation. Common applications include:

1. Indoor Irrigation Systems – Used when a PVB would be unsuitable due to potential water discharge, such as in greenhouses or indoor sprinkler systems.
2. Commercial Beverage Equipment – Protects water supplies in soda machines, coffee makers, and other food-service equipment where spills could be problematic.
3. Medical & Dental Equipment – Applied in water supply lines for autoclaves, dental chairs, and lab equipment to prevent back-siphonage while avoiding leaks.
4. Hydroponic & Agricultural Systems – Used in indoor plant watering systems where spills could damage sensitive areas.
5. HVAC Humidifiers – Protects potable water connections in steam humidifiers, preventing siphoning without causing leaks.

Important Considerations:

✔️ Must be installed above the highest downstream outlet (like a PVB).

✔️ Protects against back-siphonage but not backpressure, making it unsuitable for systems where downstream pressure could push contaminants back.

✔️ Designed for locations where water spillage could cause damage, unlike a standard PVB, which can release water during operation.

If back-siphonage and backpressure protection are needed, an RPZ or DCVA is typically required instead.