Chapter 5, mechanisms for preventing backflow Flashcards
1
Q
Air gaps are usually the cheapest form of backflow prevention, true or false?
A
True
2
Q
Where Airgas cannot be used, these these assemblies provide a physical barrier to backflow
A
Mechanical backflow preventers
3
Q
Two methods of non-mechanical backflow prevention are:
A
Air Gaps and Barometric Loops
4
Q
A _____ is a mechanical way to protect against backflow.
A
Device
5
Q
This term is referred to as the entire backflow prevention unit, including the mechanism that actually prevent backflow, but also the shut off valves and test cocks
A
Assembly
6
Q
What term refers to the backflow prevention mechanism only, it does not include the shut off valves.
A
Device
7
Q
Approved assemblies must be shipped from the manufacturer as:
A
One complete unit
8
Q
What foundation at the University of Southern California field test backflow assemblies?
A
The foundation for cross connection, control, and hydraulic research
9
Q
The backflow preventer must also have shut off valves that have a:
A
Full flow characteristic
10
Q
Potential is the essential factor. The purpose is to eliminate unnecessary reduction in pressure since backflow preventer themselves already reduced pressure… true or false
A
True
11
Q
This term is defined as capable of withstanding shock without permanent deformation rupture.
A
Resilient seated
12
Q
A resilient seated valve usually contains some form of soft rubber or other flexible material that can:
A
Withstand shock
13
Q
Shut off valves that are resilient seated are usually designated with what character or characters?
A
“R” or “RS”
14
Q
The operating stem on a ball valve type test cock must be:
A
Blowout proof
15
Q
To be approved, a backflow preventer must be testable and repairable:
A
In-line
16
Q
Being repairable in-line means that the backflow preventer must be
A
Stay in place
17
Q
These are the simplest type of mechanical backflow prevention.
A
Atmospheric vacuum breakers (AVBs)
18
Q
Atmospheric vacuum breakers can be tested in line. True or false.
A
False
19
Q
Atmospheric vacuum breakers can be used to protect against _______ only
A
Back siphonage
20
Q
The AVB contains a single disc float, also known as a:
A
Poppet valve
21
Q
AVB’s are NOT approved for use where they will be subject to
A
Continuous pressure in the direction of flow
22
Q
Shut off valves are not allowed downstream of
A
AVB’s
23
Q
After _______ or more hours of continuous pressure, the float can become permanently stuck to the air in the port
A
12 to 14
24
Q
What is the image a picture of?
A
An atmospheric vacuum breaker.
25
When turning the water off to an atmosphere vacuum breaker, how can it be determined if the float disk is working?
It can be heard as it falls
26
What is the minimum height that a vacuum breaker must be installed to the underside of its body above the highest outlet?
6 inches
27
Back for pool runners are required to include an air that indicates the direction of flow in order to be designated what?
Approved
28
The AVB must never be subject to ________ , since it relies on atmospheric pressure to function
Flooding
29
True or false AVB provide protection against back pressure
False
30
This is an atmospheric vacuum breaker that has been adapted to fit on a hose bib or sill cock
Hose bib vacuum breaker
31
What is the image of picture of?
A pressure vacuum breaker
32
The pressure vacuum breaker is an ________ instead of a device, it has to shut off valves and two tests.
Assembly
33
On a pressure vacuum breaker the air inlet and the check valve operate _______ each other
Independently
34
The AWA specification for a spring loaded, soft seated check valve is that it must be drip tight and hold______ in the direction of flow
1.0 PSI
35
Generally, the PVB is used for_______. For instance, it is commonly used on lawn irrigation systems
Isolation
36
Unlike the AVB, the PVB can be used where it will be subjected to:
Continuous pressure
37
True or false because the PVB can be subjected to continuous pressure, it is acceptable to have a shut off valve downstream of the assembly.
True
38
The PVB cannot be subjected to
Back pressure
39
For a PVB, the minimum height Between the bottom of the critical level and the highest point in the system.
12 inches
40
Lawn irrigation systems are classified as a:
High Hazard
41
Similar to PVB’s these type of vacuum breakers have two shut off valves, one test cock, and one bleed screw
Spill resistant vacuum breakers.
42
True or false the SVB does not discharge water when the assembly is pressurized
True
43
The critical level of a SBV is usually located at the opening of the
Check valve
44
The springs in a ______ are identical, and sometimes interchangeable
Double check valve assembly
45
According to AWWA specifications, the springs inside of a double check valve assembly should hold drip tight against
One PSI in the normal direction of flow
46
According to a WWE specifications, the springs inside of a double check valve assembly should hold drip tight against
One PSI in the normal direction of flow
47
The maximum pressure drop out across a double check valve assembly is:
10 psi
48
True or false double check valves do not provide adequate protection against both types of backflow: back siphonage, and back pressure
False
49
Double check valve assemblies can be subjected to continuous pressure. Under normal flow conditions, the first check valve effectively reduces the supply line pressure by what range?
1.0 to 5.0 psi
50
The maximum pressure loss allowed across a DC VA cannot exceeded:
10 psi
51
Double check valve assemblies are only approved for
Low or non-Health hazard situations
52
DCVAs are traditional used _______ and are installed after the meter or at the point of service
For isolation
53
Double check valve assemblies should be installed at least ______ and at most _____ above the ground, drainage system, or flood elevation
12 inches to 36 inches
54
True or false, double check valve assemblies may be installed inside of vaults
True
55
Vault installations are considered to be:
Confined spaces
56
These are the only approved backflow preventers that can be installed below ground. This installation is usually discouraged.
Double check valve assemblies
57
What is this a picture of?
Reduced pressure principle assembly
58
On an RP, the first check valve is designed to reduce water pressure by a minimum of approximately:
5.0 psi
59
On an RP the second second check valve is only designed to hold back a minimum of:
1.0 psi
60
Inside of a RP a _____ is created that will not allow water to backflow
Hydraulic gradient
61
On an RP the area between the first check valve and the second check valve is referred to as what?
The reduced pressure zone
62
When the relief valve opens to the atmosphere, it provides what between the two check valves?
An air gap
63
The spring on an RP relief valve is designed to provide a minimum pressure of
2.0 psi
64
Under normal operating conditions, the pressure inside the reduce pressure zone is approximately ________ less than the pressure on the supply side of the first check
5.0 to 12.0 PSI
65
The 5.0 psi deficiency between the high side pressure and the zone pressure allows for some:
Fluctuation in the line pressure
66
Because the relief foul provides edit protection, the RP is considered adequate for:
High and low hazards
67
The RP is considered the most ________ backflip as it can be used in all situations except for inside of a vault
Versatile
68
The RP should be installed so that the vent of the differential relief valve is at least ________ no more than ______ above grade
12 inches, 36 inches
69
AARP should have a minimum clearance________ on all sides
24”
70
If a drain line is installed on the relief port a ______ should be provided to avoid creating a cross connection between the assembly and the drain
Manufactured air gap
71
______ is caused by air in the system or fluctuations in line pressure
Spitting
72
If there is a loss in supply line pressure to the RP, what happens?
It dumps the zone
73
A steady drip or continuous flow of water from the vent indicates that the RP is:
Not working properly
74
There must be a minimum separation of two times the affected area or inside pipe diameter, of the water supply outlet between the outlet and the:
Flood level rim
75
What is the absolute minimum that must be maintained for an airgap?
1 inch
76
______ is the attraction of unlike particles.
Adhesion
77
_______ is the attraction of like particles
Cohesion
78
_______ is the attraction of like particles
Cohesion
79
If the water supply outlet is adjacent to a sidewall, within three diameters of the water supply outlet, the minimum air gap must be
Three times the inside diameter of the outlet pipe
80
A barometric loop of 34 feet high is effective against what form of backflow only?
Back siphonage
81
A single check valve is not considered a:
Adequate form of backflow prevention
82
A single check valve cannot be tested:
In line
83
Dual in-line check valves that cannot be tested. Have a _______ failure rate for both checks within the first five years.
50%
84
This type of check is designed to detect small weeks or illegal water usage that cannot be detected by the less sensitive meter installed on the large line upstream from this assembly
Detector check
85
This type of check is designed to detect small weeks or illegal water usage that cannot be detected by the less sensitive meter installed on the large line upstream from this assembly
Detector check
86
What is the image a picture of?
A double check detector assembly
87
The maximum pressure loss through a double check detector assembly is:
10psi
88
For a double detector check assembly the first spring must hold drip tight against
1.0 psi regardless of the size of assembly
89
What is the maximum size of a reduced pressure detector assembly?
10 inches
90
What is the maximum size of a reduced pressure detector assembly?
10 inches
91
Where are reduced pressure detector assemblies frequently used?
Fire sprinkler systems
92
If a fire sprinkler system does not have any additives and has no chance for auxiliary water supply to be connected then the system is considered
Low hazard
93
For low hazard fire sprinkler systems what is considered the appropriate assembly?
A double detector check
94
A detector bypass on a backflow prevention assembly is not necessary if the fire protection system has an
Operating alarm that will indicate if water is flowing
95
Reduced pressure detector assemblies average about ________ PSI pressure loss
13 or 14
96
Regular RPZ assemblies about _______ pressure loss
10 psi
97
Prior to installation, the waterline should be_______ to remove loose materials that could foul the backflow preventer
Thoroughly flushed
98
True or false sometimes it is recommended that a strainer be located prior to the assembly to trap any loose materials that could otherwise file the assembly
True
99
True or false, providing a blow off valve after the backflow preventer is not a good idea
False, the blow off valve can be used to remove grease and form materials that are produced when repairing the assembly, or to flush the customers waterline of any contaminants after a backflow incident without contaminating the backflow preventer
100
True or false, providing a blow off valve after the backflow preventer is not a good idea
False, the blow off valve can be used to remove grease and form materials that are produced when repairing the assembly, or to flush the customers waterline of any contaminants after a backflow incident without contaminating the backflow preventer
101
This is the increase in pressure in a closed water system due to heating and expanding water
Thermal expansion
102
This is the increase in pressure in a closed water system due to heating and expanding water
Thermal expansion
103
For proper function, T and P valves need to be
Exercised regularly
104
Well, almost backflow preventers may withstand freezing temperatures for short period of time, anytime over what can burst the assembly?
10 hours
105
To prevent freezing, the customer should either_______ or ________
Enclose the assembly with a heat source, or continuously run water
106
Backflow preventer should be rebuilt or replaced every?
Five years
107
Records concerning variance or exemption granted to the system shall be kept for a period and they not less than
Five years following the expiration of the variance and exemption
108
Any systems subject to the requirements of rule 62–550.800, F. A. C. Shall retain no fewer than how many years original records.
12 years
