Q1: What is backflow?
ANSWER Backflow is the undesirable reversal of flow of water or other
substances from any source back into the potable water supply system.
Q2: What are the two main causes of backflow?
ANSWER Backpressure and backsiphonage are the two main causes of
backflow.
Q3: What is backsiphonage?
ANSWER Backsiphonage occurs when negative pressure (vacuum or
partial vacuum) in a supply line draws contaminants back into the potable
water system.
Q4: What is backpressure?
ANSWER Backpressure occurs when the downstream pressure exceeds
the supply pressure, forcing contaminants back into the potable water
supply.
Q5: What is a cross-connection?
ANSWER A cross-connection is any actual or potential connection
between the potable water supply and a source of contamination or
pollution.
Q6: What is the difference between a contaminant and a pollutant in
backflow terms?
ANSWER A contaminant poses a health hazard (biological, chemical, or
radiological), while a pollutant is a substance that degrades water quality
but does not necessarily cause a health hazard.
Q7: What is the potable water supply?
Backflow Prevention — 300 Q&A Study Guide | Page 1
, ANSWER The potable water supply is water that meets drinking water
standards and is safe for human consumption.
Q8: What is the purpose of a backflow prevention assembly?
ANSWER A backflow prevention assembly protects the potable water
supply from contamination or pollution due to backflow.
Q9: What does the term 'health hazard' mean in cross-connection
control?
ANSWER A health hazard refers to any condition, device, or practice that
may create a danger to the physical well-being of a person, including
biological, chemical, or radiological contamination.
Q10: What is a direct cross-connection?
ANSWER A direct cross-connection is a physical connection between the
potable water system and a non-potable source that is always present.
Q11: What is an indirect cross-connection?
ANSWER An indirect cross-connection is a potential connection that
exists only under certain conditions, such as a submerged inlet.
Q12: Why is backflow prevention important?
ANSWER Backflow prevention protects public health by ensuring that
drinking water supplies are not contaminated by pollutants or pathogens
from non-potable sources.
Q13: What organization sets national standards for backflow
prevention assemblies in the US?
ANSWER The American Society of Sanitary Engineering (ASSE) and the
University of Southern California Foundation for Cross-Connection Control
and Hydraulic Research (USC FCCCHR) set key standards.
Q14: What is a high-hazard cross-connection?
ANSWER A high-hazard cross-connection is one where backflow could
introduce substances that are dangerous to health into the potable water
supply.
Q15: What is a low-hazard cross-connection?
ANSWER A low-hazard cross-connection involves a substance that may
affect the taste, odor, or color of water but does not pose a health risk.
Q16: What is the 'zone of health hazard' in cross-connection control?
Backflow Prevention — 300 Q&A Study Guide | Page 2
, ANSWER The zone of health hazard is the area or system containing
water or substances that could be dangerous to health if introduced into the
potable water supply.
Q17: What is meant by 'degree of hazard' in backflow prevention?
ANSWER The degree of hazard refers to the severity of the risk posed by
a potential backflow situation, which determines the level of protection
required.
Q18: What is the USC FCCCHR?
ANSWER The University of Southern California Foundation for Cross-
Connection Control and Hydraulic Research is a leading authority that
develops standards and testing protocols for backflow prevention
assemblies.
Q19: What is a non-potable water system?
ANSWER A non-potable water system carries water that is not safe for
drinking, such as irrigation water, recycled water, or industrial process
water.
Q20: What is meant by 'protection in proportion to the degree of
hazard'?
ANSWER This principle means that the level of backflow protection
installed must match the severity of the hazard posed by the cross-
connection.
───────────────────────────────────────────────
─────────────────────────────────
2. Types of Backflow Prevention Assemblies
Q21: What is an air gap?
ANSWER An air gap is a physical separation between the water supply
outlet and the flood level rim of a receiving vessel, providing the highest
level of backflow protection.
Q22: What is the minimum air gap distance required?
ANSWER The minimum air gap is twice the diameter of the supply pipe,
but never less than 1 inch.
Q23: What is a Reduced Pressure Zone assembly (RPZ)?
ANSWER An RPZ is a backflow prevention assembly that uses two
independently acting check valves and a differential pressure relief valve to
Backflow Prevention — 300 Q&A Study Guide | Page 3
ANSWER Backflow is the undesirable reversal of flow of water or other
substances from any source back into the potable water supply system.
Q2: What are the two main causes of backflow?
ANSWER Backpressure and backsiphonage are the two main causes of
backflow.
Q3: What is backsiphonage?
ANSWER Backsiphonage occurs when negative pressure (vacuum or
partial vacuum) in a supply line draws contaminants back into the potable
water system.
Q4: What is backpressure?
ANSWER Backpressure occurs when the downstream pressure exceeds
the supply pressure, forcing contaminants back into the potable water
supply.
Q5: What is a cross-connection?
ANSWER A cross-connection is any actual or potential connection
between the potable water supply and a source of contamination or
pollution.
Q6: What is the difference between a contaminant and a pollutant in
backflow terms?
ANSWER A contaminant poses a health hazard (biological, chemical, or
radiological), while a pollutant is a substance that degrades water quality
but does not necessarily cause a health hazard.
Q7: What is the potable water supply?
Backflow Prevention — 300 Q&A Study Guide | Page 1
, ANSWER The potable water supply is water that meets drinking water
standards and is safe for human consumption.
Q8: What is the purpose of a backflow prevention assembly?
ANSWER A backflow prevention assembly protects the potable water
supply from contamination or pollution due to backflow.
Q9: What does the term 'health hazard' mean in cross-connection
control?
ANSWER A health hazard refers to any condition, device, or practice that
may create a danger to the physical well-being of a person, including
biological, chemical, or radiological contamination.
Q10: What is a direct cross-connection?
ANSWER A direct cross-connection is a physical connection between the
potable water system and a non-potable source that is always present.
Q11: What is an indirect cross-connection?
ANSWER An indirect cross-connection is a potential connection that
exists only under certain conditions, such as a submerged inlet.
Q12: Why is backflow prevention important?
ANSWER Backflow prevention protects public health by ensuring that
drinking water supplies are not contaminated by pollutants or pathogens
from non-potable sources.
Q13: What organization sets national standards for backflow
prevention assemblies in the US?
ANSWER The American Society of Sanitary Engineering (ASSE) and the
University of Southern California Foundation for Cross-Connection Control
and Hydraulic Research (USC FCCCHR) set key standards.
Q14: What is a high-hazard cross-connection?
ANSWER A high-hazard cross-connection is one where backflow could
introduce substances that are dangerous to health into the potable water
supply.
Q15: What is a low-hazard cross-connection?
ANSWER A low-hazard cross-connection involves a substance that may
affect the taste, odor, or color of water but does not pose a health risk.
Q16: What is the 'zone of health hazard' in cross-connection control?
Backflow Prevention — 300 Q&A Study Guide | Page 2
, ANSWER The zone of health hazard is the area or system containing
water or substances that could be dangerous to health if introduced into the
potable water supply.
Q17: What is meant by 'degree of hazard' in backflow prevention?
ANSWER The degree of hazard refers to the severity of the risk posed by
a potential backflow situation, which determines the level of protection
required.
Q18: What is the USC FCCCHR?
ANSWER The University of Southern California Foundation for Cross-
Connection Control and Hydraulic Research is a leading authority that
develops standards and testing protocols for backflow prevention
assemblies.
Q19: What is a non-potable water system?
ANSWER A non-potable water system carries water that is not safe for
drinking, such as irrigation water, recycled water, or industrial process
water.
Q20: What is meant by 'protection in proportion to the degree of
hazard'?
ANSWER This principle means that the level of backflow protection
installed must match the severity of the hazard posed by the cross-
connection.
───────────────────────────────────────────────
─────────────────────────────────
2. Types of Backflow Prevention Assemblies
Q21: What is an air gap?
ANSWER An air gap is a physical separation between the water supply
outlet and the flood level rim of a receiving vessel, providing the highest
level of backflow protection.
Q22: What is the minimum air gap distance required?
ANSWER The minimum air gap is twice the diameter of the supply pipe,
but never less than 1 inch.
Q23: What is a Reduced Pressure Zone assembly (RPZ)?
ANSWER An RPZ is a backflow prevention assembly that uses two
independently acting check valves and a differential pressure relief valve to
Backflow Prevention — 300 Q&A Study Guide | Page 3
