BACKFLOW PREVENTION ASSEMBLY TESTER EXAM
QUESTIONS WITH VERIFIED SOLUTIONS - UPDATED
VERSION 2026/2027
1. What is backflow?
Answer: Backflow is the undesirable reversal of flow of water or other
substances from any source back into the potable water distribution system.
2. What are the two types of backflow?
Answer: The two types of backflow are back-siphonage and back-pressure.
3. What causes back-siphonage?
Answer: Back-siphonage is caused by a negative pressure (vacuum or partial
vacuum) in the supply piping, which creates a siphon effect that draws non-
potable water back into the potable system.
4. What causes back-pressure?
Answer: Back-pressure is caused when the downstream pressure exceeds
the supply pressure, forcing non-potable water backward into the potable
supply. Common causes include pumps, thermal expansion, or elevated
piping.
5. What is a cross-connection?
Answer: A cross-connection is any actual or potential connection between the
potable water supply and any source of contamination or pollution, which
could allow backflow to occur.
6. What is the purpose of a backflow preventer?
Answer: A backflow preventer is a mechanical device or assembly designed
to prevent the reverse flow of water from a potentially contaminated source
back into the potable water supply.
7. What is the USC Manual of Cross-Connection Control?
Answer: The USC Manual (University of Southern California) is a nationally
recognized guide for cross-connection control programs, providing standards
and procedures for backflow prevention.
Backflow Prevention — 260 Questions & Answers
,8. What does AWWA stand for?
Answer: AWWA stands for the American Water Works Association, a
nonprofit organization that sets standards and guidelines for the water utility
industry.
9. What is the degree of hazard?
Answer: The degree of hazard refers to the potential risk that a cross-
connection poses to the public water supply, classified as either a health
hazard or a non-health (plumbing/pollutant) hazard.
10. What is a health hazard cross-connection?
Answer: A health hazard cross-connection is one where the contaminant or
pollutant could cause illness, injury, or death if it enters the potable water
supply (e.g., chemicals, sewage, or toxic substances).
11. What is a non-health hazard (pollutant) cross-connection?
Answer: A non-health hazard is a cross-connection involving a substance that
would be objectionable but not a threat to health (e.g., food products, non-
toxic fluids) that degrades water quality.
12. What is the definition of potable water?
Answer: Potable water is water that is safe for human consumption — free
from harmful contaminants in concentrations that could cause disease or
illness.
13. What organization typically enforces cross-connection control
programs?
Answer: Cross-connection control programs are typically enforced by the
local water purveyor (water utility), often in conjunction with local health
departments and plumbing codes.
14. What is a water purveyor?
Answer: A water purveyor is any person or organization (public or private)
that owns or operates a public water supply system.
15. What is the primary law governing safe drinking water in the United
States?
Answer: The Safe Drinking Water Act (SDWA), enacted in 1974 and
amended multiple times, is the primary federal law protecting public drinking
water supplies in the United States.
16. What does EPA stand for in water treatment?
Backflow Prevention — 260 Questions & Answers
, Answer: EPA stands for the Environmental Protection Agency, the federal
agency responsible for regulating and enforcing environmental laws including
water quality standards.
17. What is containment (premise isolation)?
Answer: Containment, or premise isolation, is a cross-connection control
method where a backflow preventer is installed at the water meter or service
connection to isolate the entire premises from the public water main.
18. What is internal protection in cross-connection control?
Answer: Internal protection involves installing backflow prevention devices at
specific cross-connections within a facility, rather than just at the service
connection.
19. What is an air gap?
Answer: An air gap is the vertical physical separation between the water
supply outlet and the overflow rim of a receiving vessel, providing absolute
protection against backflow. The minimum required is two times the diameter
of the supply pipe or 1 inch, whichever is greater.
20. What is the minimum air gap distance required by most codes?
Answer: Most codes require the air gap to be a minimum of twice the
diameter of the supply pipe or at least 1 inch (25.4 mm), whichever is greater.
21. Name the four main types of mechanical backflow prevention
assemblies.
Answer: The four main types are: (1) Air Gap (AG), (2) Atmospheric Vacuum
Breaker (AVB), (3) Pressure Vacuum Breaker Assembly (PVB), (4) Double
Check Valve Assembly (DC), and (5) Reduced Pressure Principle Assembly
(RP).
22. What does RP stand for in backflow prevention?
Answer: RP stands for Reduced Pressure Principle Assembly (also called
Reduced Pressure Zone Assembly or RPZ), a mechanical assembly that
provides the highest level of protection among testable assemblies.
23. What does DC stand for in backflow prevention?
Answer: DC stands for Double Check Valve Assembly, a testable backflow
prevention assembly suitable for protection against low-to-moderate hazard
cross-connections.
24. What is a Pressure Vacuum Breaker (PVB)?
Answer: A Pressure Vacuum Breaker Assembly is a testable device
containing a spring-loaded check valve and an air inlet valve designed to
Backflow Prevention — 260 Questions & Answers
, prevent back-siphonage. It must be installed at least 12 inches above the
highest downstream piping.
25. What hazard level does an RP assembly protect against?
Answer: An RP assembly protects against both high hazard (health hazard)
and low hazard conditions, and can protect against both back-siphonage and
back-pressure.
26. What hazard level does a DC assembly protect against?
Answer: A Double Check Valve Assembly protects against low hazard (non-
health hazard/pollutant) cross-connections under both back-siphonage and
back-pressure conditions.
27. Can a PVB be used against back-pressure?
Answer: No. A Pressure Vacuum Breaker Assembly is only approved for
protection against back-siphonage conditions, NOT back-pressure.
28. What is an Atmospheric Vacuum Breaker (AVB)?
Answer: An Atmospheric Vacuum Breaker is a non-testable device that
protects against back-siphonage only. It must be installed at least 6 inches
above the highest downstream outlet and cannot have shutoff valves
downstream of it.
29. What is the relief valve port on an RP assembly designed to do?
Answer: The relief valve port on an RP assembly opens to atmosphere when
the differential pressure between zone 1 and zone 2 drops below 2 PSI,
discharging water to prevent contaminated water from entering the potable
supply.
30. What is the minimum differential pressure that must be maintained
across the first check valve of an RP assembly?
Answer: The first check valve of an RP assembly must maintain a minimum
differential pressure of 5 PSI (pounds per square inch) to remain closed and
functional.
SECTION 2: REDUCED PRESSURE PRINCIPLE ASSEMBLY — RP (Q31–70)
31. Describe the components of a standard RP assembly.
Answer: A standard RP assembly consists of: two independently acting
spring-loaded check valves, a differential pressure relief valve (located
between the two checks), and two resilient-seated shutoff valves (one on each
end).
Backflow Prevention — 260 Questions & Answers
QUESTIONS WITH VERIFIED SOLUTIONS - UPDATED
VERSION 2026/2027
1. What is backflow?
Answer: Backflow is the undesirable reversal of flow of water or other
substances from any source back into the potable water distribution system.
2. What are the two types of backflow?
Answer: The two types of backflow are back-siphonage and back-pressure.
3. What causes back-siphonage?
Answer: Back-siphonage is caused by a negative pressure (vacuum or partial
vacuum) in the supply piping, which creates a siphon effect that draws non-
potable water back into the potable system.
4. What causes back-pressure?
Answer: Back-pressure is caused when the downstream pressure exceeds
the supply pressure, forcing non-potable water backward into the potable
supply. Common causes include pumps, thermal expansion, or elevated
piping.
5. What is a cross-connection?
Answer: A cross-connection is any actual or potential connection between the
potable water supply and any source of contamination or pollution, which
could allow backflow to occur.
6. What is the purpose of a backflow preventer?
Answer: A backflow preventer is a mechanical device or assembly designed
to prevent the reverse flow of water from a potentially contaminated source
back into the potable water supply.
7. What is the USC Manual of Cross-Connection Control?
Answer: The USC Manual (University of Southern California) is a nationally
recognized guide for cross-connection control programs, providing standards
and procedures for backflow prevention.
Backflow Prevention — 260 Questions & Answers
,8. What does AWWA stand for?
Answer: AWWA stands for the American Water Works Association, a
nonprofit organization that sets standards and guidelines for the water utility
industry.
9. What is the degree of hazard?
Answer: The degree of hazard refers to the potential risk that a cross-
connection poses to the public water supply, classified as either a health
hazard or a non-health (plumbing/pollutant) hazard.
10. What is a health hazard cross-connection?
Answer: A health hazard cross-connection is one where the contaminant or
pollutant could cause illness, injury, or death if it enters the potable water
supply (e.g., chemicals, sewage, or toxic substances).
11. What is a non-health hazard (pollutant) cross-connection?
Answer: A non-health hazard is a cross-connection involving a substance that
would be objectionable but not a threat to health (e.g., food products, non-
toxic fluids) that degrades water quality.
12. What is the definition of potable water?
Answer: Potable water is water that is safe for human consumption — free
from harmful contaminants in concentrations that could cause disease or
illness.
13. What organization typically enforces cross-connection control
programs?
Answer: Cross-connection control programs are typically enforced by the
local water purveyor (water utility), often in conjunction with local health
departments and plumbing codes.
14. What is a water purveyor?
Answer: A water purveyor is any person or organization (public or private)
that owns or operates a public water supply system.
15. What is the primary law governing safe drinking water in the United
States?
Answer: The Safe Drinking Water Act (SDWA), enacted in 1974 and
amended multiple times, is the primary federal law protecting public drinking
water supplies in the United States.
16. What does EPA stand for in water treatment?
Backflow Prevention — 260 Questions & Answers
, Answer: EPA stands for the Environmental Protection Agency, the federal
agency responsible for regulating and enforcing environmental laws including
water quality standards.
17. What is containment (premise isolation)?
Answer: Containment, or premise isolation, is a cross-connection control
method where a backflow preventer is installed at the water meter or service
connection to isolate the entire premises from the public water main.
18. What is internal protection in cross-connection control?
Answer: Internal protection involves installing backflow prevention devices at
specific cross-connections within a facility, rather than just at the service
connection.
19. What is an air gap?
Answer: An air gap is the vertical physical separation between the water
supply outlet and the overflow rim of a receiving vessel, providing absolute
protection against backflow. The minimum required is two times the diameter
of the supply pipe or 1 inch, whichever is greater.
20. What is the minimum air gap distance required by most codes?
Answer: Most codes require the air gap to be a minimum of twice the
diameter of the supply pipe or at least 1 inch (25.4 mm), whichever is greater.
21. Name the four main types of mechanical backflow prevention
assemblies.
Answer: The four main types are: (1) Air Gap (AG), (2) Atmospheric Vacuum
Breaker (AVB), (3) Pressure Vacuum Breaker Assembly (PVB), (4) Double
Check Valve Assembly (DC), and (5) Reduced Pressure Principle Assembly
(RP).
22. What does RP stand for in backflow prevention?
Answer: RP stands for Reduced Pressure Principle Assembly (also called
Reduced Pressure Zone Assembly or RPZ), a mechanical assembly that
provides the highest level of protection among testable assemblies.
23. What does DC stand for in backflow prevention?
Answer: DC stands for Double Check Valve Assembly, a testable backflow
prevention assembly suitable for protection against low-to-moderate hazard
cross-connections.
24. What is a Pressure Vacuum Breaker (PVB)?
Answer: A Pressure Vacuum Breaker Assembly is a testable device
containing a spring-loaded check valve and an air inlet valve designed to
Backflow Prevention — 260 Questions & Answers
, prevent back-siphonage. It must be installed at least 12 inches above the
highest downstream piping.
25. What hazard level does an RP assembly protect against?
Answer: An RP assembly protects against both high hazard (health hazard)
and low hazard conditions, and can protect against both back-siphonage and
back-pressure.
26. What hazard level does a DC assembly protect against?
Answer: A Double Check Valve Assembly protects against low hazard (non-
health hazard/pollutant) cross-connections under both back-siphonage and
back-pressure conditions.
27. Can a PVB be used against back-pressure?
Answer: No. A Pressure Vacuum Breaker Assembly is only approved for
protection against back-siphonage conditions, NOT back-pressure.
28. What is an Atmospheric Vacuum Breaker (AVB)?
Answer: An Atmospheric Vacuum Breaker is a non-testable device that
protects against back-siphonage only. It must be installed at least 6 inches
above the highest downstream outlet and cannot have shutoff valves
downstream of it.
29. What is the relief valve port on an RP assembly designed to do?
Answer: The relief valve port on an RP assembly opens to atmosphere when
the differential pressure between zone 1 and zone 2 drops below 2 PSI,
discharging water to prevent contaminated water from entering the potable
supply.
30. What is the minimum differential pressure that must be maintained
across the first check valve of an RP assembly?
Answer: The first check valve of an RP assembly must maintain a minimum
differential pressure of 5 PSI (pounds per square inch) to remain closed and
functional.
SECTION 2: REDUCED PRESSURE PRINCIPLE ASSEMBLY — RP (Q31–70)
31. Describe the components of a standard RP assembly.
Answer: A standard RP assembly consists of: two independently acting
spring-loaded check valves, a differential pressure relief valve (located
between the two checks), and two resilient-seated shutoff valves (one on each
end).
Backflow Prevention — 260 Questions & Answers
