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Backflow > Assemblies > Flashcards

Assemblies Flashcards

Learn the four different backflow prevention assemblies

1
Q

Which assembly has only one test cock?

A

SVB

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2
Q

Which assembly has four shut offs, four checks & 8 test cocks?

A

DCDA

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3
Q

Maximum allowable pressure loss across a Double check assembly?

A

10 PSIG

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4
Q

It is recommended that a DC be installed with its critical level a minimum of ____ inches above the floor?

A

12inches

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5
Q

What is the minimum pressure drop across each check of a DC in a static condition?

A

1.0 PSID

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6
Q

Where is the #2 test cock of a DC located?

A

upstream of check valve #1

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7
Q

What is considered to be critical level of a PVB if it is not marked?

A

The bottom of the valve body

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8
Q

What can be done if the air inlet valve of a PVB will not seat?

A

Increase the supply pressure

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9
Q

What is the reason for the meter on a DCDA ?

A

To detect unauthorized water usage

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10
Q

A DC may be used for what type of hazard only?

A

Low

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11
Q

The purpose of the bypass flow indicator is to detect low flow rates up to how many GPM ?

A

2GPM

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12
Q

The PVB shut-off valves are located where on the assembly?

A

At the inlet and outlet of the assembly

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13
Q

A DC consists of how many valves & checks?

A

2 of each

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14
Q

Are the checks of a DC interchangeable?

A

YES

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15
Q

Where is the #1 test cock located on a PVB?

A

Upstream of the check

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16
Q

Can the PVB & SVB be subjected to continuous pressure?

A

YES

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17
Q

What is the critical level of a PVB or SVB?

A

12 inches above the highest downstream use.

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18
Q

How many test cocks does a PVB have on the assembly?

A

2 test cocks

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19
Q

How many test cocks does an SVB have on the assembly?

A

One test cock

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20
Q

An SVB ‘s check must be drip-tight at ?

A

1.0 PSID

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21
Q

The opening PSID of an SVB air inlet valve is a minimum of ?

A

1.0 PSID

22
Q

What is the maximum allowable pressure drop across a PVB or SVB?

A

10 PSIG

23
Q

What is the maximum protection provide by the PVB or SVB?

A

High hazard - backsiphonage

24
Q

A characteristic of the SVB operation is that the air inlet must seal before the :

A

Check opens

25
Q

Can the PVB or SVB have valves downstream of the assembly?

A

YES

26
Q

Could a PVB or SVB be subjected to backpressure and where would the backpressure come from?

A

YES and a closed downstream valve

27
Q

The hydraulic purpose of any vacuum breaker is to stop:

A

a siphon

28
Q

What is the minimum check valve closing differential for a PVB?

A

1.0 PSID

29
Q

The springs on the 2 check valves of an RP are

A

Always loaded differently

30
Q

Why should the #2 shut-off valve be closed first when testing a DC,RP,PVB or SVB?

A

To maintain pressure in the assembly

31
Q

An enclosure around the installation of an RP must have:

A

a provision for drainage

32
Q

What cause occasional discharge of water from the relief opening on an RP?

A

A fluctuation in supply pressure

33
Q

Performance design specs of an RP requires the differential pressure across the #1 check to be at least ___PSI greater than the PSI of the relief valve.

A

3PSI

34
Q

What is the function of the spring in the relief valve of an RP ?

A

To force the relief valve open

35
Q

What is the critical level for an RP ?

A

12 inches

36
Q

The relief valve on an RP remains closed during normal operation due to:

A

Supply side pressure

37
Q

What is the purpose for flushing the test cocks on all the assemblies?

A

To remove any trash that may be in the test cock

38
Q

How can you stop an occasional discharge of water from the relief valve of an RP caused by supply pressure fluctuations?

A

Install a soft seated check valve upstream of the assembly

39
Q

Can an RP be installed in the vertical position?

A

Yes , if it has been tested and approved for that installation.

40
Q

What is the minimum differential pressure drop across the #1 check valve of an RP?

A

5 PSID

41
Q

What is the maximum protection offered by an RP ?

A

High hazard - backpressure & backsiphonage

42
Q

What is the minimum differential pressure drop across the #2 check valve of an RP?

A

1.0 PSID

43
Q

Where should an RP never be installed?

A

In a pit or a vault

44
Q

What is the minimum loading to open the relief valve of an RP?

A

2PSID

45
Q

The calculated value between the #1 check valve and the relief opening is referred to as the :

A

Buffer

46
Q

Where should a strainer be installed on an RP or DC?

A

upstream of the assembly

47
Q

Where is the #1 test cock located on an RP or DC?

A

upstream of the #1 shut-off valve

48
Q

Where is the relief opening located in the RP?

A

Between the #1 & #2 checks

49
Q

For an assembly to be approved it must be?

A

in-line testable and repairable

50
Q

Why would an RP or DC be installed in parallel?

A

when it is vital to maintain continuous water flow

Backflow (5 decks)

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