Chapter 3 Flashcards
What are the 4 things that need to be considered when determining the proper form of backflow prevention? (Did Pirates Have Fun)
1) Degree of Hazard
2) Probability of occurrence
3) Hydraulic conditions
4) Functional limitations
What is the definition of a severe hazard?
An actual or potential cross
connection involving any substance in sufficient concentration as to cause
death, spread illness or disease or contain any substance which has a high
probability of causing such an effect.
What is the definition of a moderate hazard?
An actual or potential cross
connection involving any substance that has a low probability of becoming
a severe hazard and would constitute a nuisance or be aesthetically
objectionable if introduced into the domestic water supply.
What is the definition of a minor hazard?
An actual or potential connection
between the domestic water pipe and any pipe, vat or tank intended for
carrying or holding potable water, which has a low probability of becoming
a moderate hazard.
What 2 factors increase the degree of hazard assessed to a potential CC? Which one is more serious?
1) Probability that backflow will occur
2) Level of toxicity or potential toxicity <— Greater concern
List 5 ways in which backflow prevention can be accomplished
1) Creating an approved Air Gap
2) Piping arrangement (barometric loop)
3) Approved, testable backflow preventer
4) non-testable backflow preventer
5) Approved water - using equipment w/ built in backflow prevention
What is the difference bn a backflow prevention assembly / backflow prevention device?
Assemblies are designed to be in-line testable (and repairable) and therefor are equipped with the appropriate number of shutoff valves and test cocks.
Devices are looked at to ensure working condition Ex: air gap
What types of valves of found on backflow prevention assemblies?
Resilient seated full port valves, ball valves on assemblies ½” to 2” in size,
gate valves on assemblies greater than 2” in size.
What type of backflow preventer is suggested to protect against a severe hazard?
An air gap or an RP (or RPD).
A PVB or SRPVB can be used if the backflow could only be caused only by back siphonage, not back pressure.
What type of backflow preventer is suggested to protect against a moderate hazard?
A double check valve assembly (DCVA)
A double check detector assembly (DCDA)
Non - testable backflow preventers are suitable for what type(s) of application?
Minor or Moderate hazards
When are backflow preventers tested? (6 points)
- Immediately after installation
- annually
- after re-location, repair or if compromised
- After alteration UPSTREAM of supply pipe of backflow preventer
- after backflow incident
- AHJ
What does approved backflow preventer mean?
devices that have been evaluated / meet certain standards
CSA - certifies backflow preventers
Testable backflow preventers mean what?
designed to be tested / repaired in-line
True or False: Air Gaps can be easily bypassed or eliminated.
True
