Assemblies Flashcards
Learn the four different backflow prevention assemblies
Which assembly has only one test cock?
SVB
Which assembly has four shut offs, four checks & 8 test cocks?
DCDA
Maximum allowable pressure loss across a Double check assembly?
10 PSIG
It is recommended that a DC be installed with its critical level a minimum of ____ inches above the floor?
12inches
What is the minimum pressure drop across each check of a DC in a static condition?
1.0 PSID
Where is the #2 test cock of a DC located?
upstream of check valve #1
What is considered to be critical level of a PVB if it is not marked?
The bottom of the valve body
What can be done if the air inlet valve of a PVB will not seat?
Increase the supply pressure
What is the reason for the meter on a DCDA ?
To detect unauthorized water usage
A DC may be used for what type of hazard only?
Low
The purpose of the bypass flow indicator is to detect low flow rates up to how many GPM ?
2GPM
The PVB shut-off valves are located where on the assembly?
At the inlet and outlet of the assembly
A DC consists of how many valves & checks?
2 of each
Are the checks of a DC interchangeable?
YES
Where is the #1 test cock located on a PVB?
Upstream of the check
Can the PVB & SVB be subjected to continuous pressure?
YES
What is the critical level of a PVB or SVB?
12 inches above the highest downstream use.
How many test cocks does a PVB have on the assembly?
2 test cocks
How many test cocks does an SVB have on the assembly?
One test cock
An SVB ‘s check must be drip-tight at ?
1.0 PSID
The opening PSID of an SVB air inlet valve is a minimum of ?
1.0 PSID
What is the maximum allowable pressure drop across a PVB or SVB?
10 PSIG
What is the maximum protection provide by the PVB or SVB?
High hazard - backsiphonage
A characteristic of the SVB operation is that the air inlet must seal before the :
Check opens
Can the PVB or SVB have valves downstream of the assembly?
YES
Could a PVB or SVB be subjected to backpressure and where would the backpressure come from?
YES and a closed downstream valve
The hydraulic purpose of any vacuum breaker is to stop:
a siphon
What is the minimum check valve closing differential for a PVB?
1.0 PSID
The springs on the 2 check valves of an RP are
Always loaded differently
Why should the #2 shut-off valve be closed first when testing a DC,RP,PVB or SVB?
To maintain pressure in the assembly
An enclosure around the installation of an RP must have:
a provision for drainage
What cause occasional discharge of water from the relief opening on an RP?
A fluctuation in supply pressure
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.
3PSI
What is the function of the spring in the relief valve of an RP ?
To force the relief valve open
What is the critical level for an RP ?
12 inches
The relief valve on an RP remains closed during normal operation due to:
Supply side pressure
What is the purpose for flushing the test cocks on all the assemblies?
To remove any trash that may be in the test cock
How can you stop an occasional discharge of water from the relief valve of an RP caused by supply pressure fluctuations?
Install a soft seated check valve upstream of the assembly
Can an RP be installed in the vertical position?
Yes , if it has been tested and approved for that installation.
What is the minimum differential pressure drop across the #1 check valve of an RP?
5 PSID
What is the maximum protection offered by an RP ?
High hazard - backpressure & backsiphonage
What is the minimum differential pressure drop across the #2 check valve of an RP?
1.0 PSID
Where should an RP never be installed?
In a pit or a vault
What is the minimum loading to open the relief valve of an RP?
2PSID
The calculated value between the #1 check valve and the relief opening is referred to as the :
Buffer
Where should a strainer be installed on an RP or DC?
upstream of the assembly
Where is the #1 test cock located on an RP or DC?
upstream of the #1 shut-off valve
Where is the relief opening located in the RP?
Between the #1 & #2 checks
For an assembly to be approved it must be?
in-line testable and repairable
Why would an RP or DC be installed in parallel?
when it is vital to maintain continuous water flow
