Cross Connections Flashcards
What is a Cross Connection?
Physical Connection where potable and non-potable water can mix
Ex: water softener
What is backflow?
Flows backwards
What is back-siphonage?
Reversal of normal flow due to vacuum/negative pressure
EX: car takes out fire hydrant. creates low pressure in the system locally. High rise building near by will have water flow backwards due to reduced pressure
What is backpressure?
reversal of normal flow due to downstream pressure being high
What causes backsiphonage?
Backsiphonage - Very high water demand
- fire hydrants (can pull water from other houses w/o check valve)
- main break
- booster pump failure
- tower failure
What causes backpressure?
Boilers (heat causes pressure) if not hooked up properly
Buildings with elevated tanks (sometimes in older buildings) Cecil hotel ooo scary
Other heating systems
What is the difference between a pollutant and a contaminant?
Pollutant = not a health hazard, typically aesthetic
Contaminant = Health Hazard, poison, or disease
What is an AIR GAP and how does it control a cross connection?
Air gap is a physical separation of the supply pipe by at least two pipe diameters (never less than one inch) vertically above the overflow rim of the receiving vessel
An air gap may be used to protect against a CONTAMINANT or a POLLUTANT and will protect against both BACKSIPHONAGE and BACKPRESSURE. An air gap is the only acceptable means of protecting against lethal hazards.
What is an ATMOSPHERIC VACUUM BREAKER (AVB) and how does it control a cross connection?
The AVB is always placed downstream from all shut-off valves (Like a faucet). Its air inlet valve closes when the water flows in the normal direction. But, as water ceases to flow the air inlet valve opens, thus interrupting the possible back-siphonage.
An AVB must not be used for more than 12 out of an 24 hour period. It may be used to protect against either a pollutant or a contaminant, but may only be used to protect against a BACKSIPHONAGE condition. (not backpressure)
https://www.youtube.com/watch?v=QpSY79Todzk
What is a PRESSURE VACUUM BREAKER (PVB) and how does it control a cross connection?
The PVB includes a check valve which is designed to close with the aid of a spring when flow stops
The PVB may be used to protect against a pollutant or contaminant, however, it may only be used to protect against BAKCSIPHONAGE, not backpressure.
https://www.youtube.com/watch?v=IdASRPrJKq8
What is a DOUBLE CHECK VALVE ASSEMBLY (DC) and how does it control a cross connection?
This consists of two internally loaded, independently operating check valves together with tightly closing resilient seated shut-off valves upstream and downstream of the check valves.
The DC may be used to protect against a POLLUTANT ONLY
Suitable for protection against either BACKSIPHONAGE or BACKPRESSURE
What is a DOUBLE CHECK DETECTOR ASSEMBLY and how does it control a cross connection?
The DCDA is composed of a line-sized double check valve assembly with a specific bypass meter and meter-sized double check valve assembly
Normally these assemblies are reserved for use on fire sprinkler lines
What is a BAROMETRIC LOOP and how does it control a cross connection?
only for BACKSIPHONAGE NO BACKPRESSURE
Inverted āUā 35 ft tall from last water use. 33.9 feet a siphon is possible old school.
What is a Pollutant?
Not a health hazard, typically aesthetic
What is a Pollutant?
Not a health hazard, typically aesthetic
