Double check valve
A double check valve or double check assembly (DCA) is a backflow prevention device designed to protect water supplies from contamination.[1] It is different from the two-way check valves (sometimes erroneously referred to as double check valves) used in air brake systems on heavy trucks which select from the highest pressure source.
It consists of two check valves assembled in series.[2] This employs two operating principles: firstly one check valve will still act, even if the other is jammed wide open. Secondly the closure of one valve reduces the pressure differential across the other, allowing a more reliable seal and avoiding even minor leakage.
Small valves may be so compact as to be barely noticeable particularly when they are integrated into the bodies of existing taps (faucets). Larger check valves may be installed with ball valves at the ends, for isolation and testing. Often, test cocks (very small ball valves) are in place to attach test equipment for evaluating whether the double check assembly is still functional.
The double check valve assembly is suitable for prevention of back pressure and back siphonage, but is not suitable for high hazard applications. It is commonly used on lawn irrigation, fire sprinkler[2] and combi-boiler systems.[3] If the hazard is higher, even a relatively low hazard such as using antifreeze in the fire sprinkler system, then a more reliable check valve such as a reduced pressure zone device may be mandated.
Dual check valve
A dual check backflow preventer is similar to a double check valve in operation. It has two independent spring-loaded check valves. However, dual check valves usually do not include shutoff valves, may or may not be equipped with test cocks or ports, and is generally less reliable than a double check valve.[4]
See also
- Air gap
- Hydrostatic loop
- Pressure vacuum breaker
- Chemigation valve
- Reduced pressure principle BFP
- Atmospheric vacuum breaker
- Reduced pressure zone device
- Air brake (road vehicle)
References
- ^ Dietmar Findeisen (2005) Ölhydraulik: Handbuch für die hydrostatische Leistungsübertragung in der Fluidtechnik; 5. Auflage; Springer Verlag; ISBN 978-3-540-23880-5; Seite 637; Online
- ^ a b "Double Check Detector Assembly article, portlandoregon.gov". portlandoregon.gov. Retrieved 2024-03-26.
- ^ "ASHRAE Terminology". xp20.ashrae.org. ASHRAE Technical Committee. Retrieved 2022-07-27.
- ^ "Cross Connection Control and Backflow Prevention Program | Florida Department of Environmental Protection". floridadep.gov. Retrieved 2021-05-16.
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concepts
- Air gap (plumbing)
- Backflow
- Compatibility (chemical)
- Corrosion
- Drain (plumbing)
- Drinking water
- Fuel gas
- Friction loss
- Grade (slope)
- Greywater
- Heat trap
- Hydrostatic loop
- Leak
- Neutral axis
- Onsite sewage facility
- Pressure
- Sanitary sewer
- Sewer gas
- Sewage
- Sewerage
- Siphon
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- Stormwater
- Surface tension
- Tap water
- Thermal expansion
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- Thermosiphon
- Trap (plumbing)
- Venturi effect
- Wastewater
- Water hammer
- Water supply network
- Water table
- Well
- Brazing
- British Standard Pipe (BSP)
- Cast iron pipe
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- Compression fitting
- Copper tubing
- Crimp (joining)
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- Ductile iron pipe
- Flare fitting
- Garden Hose Thread (GHT)
- Gasket
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- Leak detection
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- Nominal Pipe Size (NPS)
- O-ring
- Oakum
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- Pipe dope
- Pipe support
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- Putty
- Sealant
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- Soldering
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- Swaging
- Thread seal tape
- Threaded pipe
- Tube bending
- Water heat recycling
- Atmospheric vacuum breaker
- Automatic bleeding valve
- Automatic faucet
- Backflow prevention device
- Ball valve
- Bleed screw
- Booster pump
- Butterfly valve
- Check valve
- Chemigation valve
- Chopper pump
- Circulator pump
- Cistern
- Closet flange
- Concentric reducer
- Condensate pump
- Coupling (piping)
- Diaphragm valve
- Dielectric union
- Double check valve
- Eccentric reducer
- Expansion tank
- Faucet aerator
- Float switch
- Float valve
- Floor drain
- Flow limiter
- Flushing trough
- Flushometer
- Gate valve
- Globe valve
- Grease trap
- Grinder pump
- Hose coupling
- Manifold
- Needle valve
- Nipple (plumbing)
- Pinch valve
- Piping and plumbing fitting
- Plug (sanitation)
- Pressure regulator
- Pressure vacuum breaker
- Pressure-balanced valve
- Pump
- Radiator (heating)
- Reduced pressure zone device
- Reducer
- Relief valve
- Riser clamp
- Rooftop water tower
- Safety valve
- Sewage pump
- Street elbow
- Submersible pump
- Tap (valve)
- Thermostatic mixing valve
- Trench drain
- Vacuum breaker
- Vacuum ejector
- Valve
- Water tank
- Zone valve
- Accessible bathtub
- Bathtub
- Bidet
- Dehumidifier
- Dishwasher
- Drinking fountain
- Electric water boiler
- Evaporative cooler
- Flush toilet
- Garbage disposal unit
- Hot water storage tank
- Humidifier
- Icemaker
- Instant hot water dispenser
- Laundry tub
- Shower
- Sink
- Storage water heater
- Sump pump
- Tankless water heater
- Urinal
- Washing machine
- Washlet
- Water dispenser
- Water filter
- Water heater
- Water softener
and control
trades,
and services
organizations
and standards
- Fire sprinkler system
- Piping
- Template:HVAC
- Template:Public health
- Template:Sewerage
- Template:Toilets
- Template:Wastewater
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