Chapter 4 - Backflow preventers Flashcards by Erica Keating

What is the definition of an air gap?

Is the unobstructed vertical distance through air bn the lowest pt of a water supply / flood level rim of fixture or vessel

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What are the measurements of an air gap?

2x pipe diameter
min 1 “

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What are the 3 downsides to the use of an air gap?

1) Does not guarantee continuous protection
2) Not always practical
3) easily bypassed

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Are approved air gaps required to be included in a yearly testing program?

Yes

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Are air gaps usually accompanied by the installation of an RP for area isolation?

Yes

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The reduced pressure principle backflow prevention assembly (RP) consists of what?

2 indy acting internally loaded CV
Reduced pressure zone
Pressure diff relief value
2 - shut off valves
4 test cocks

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What does the “D” stand for in RPD?

Detector

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What is the difference bn RP and RPD?

RPD has everything a RP has, plus additional RP / water meter in a bypass configuration

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What are the hazards / hydraulics that an RP / RPD protects against?

Hazards: Minor, Moderate, Severe
Hydraulics: Con’t pressure, Back pressure, Back siphonage

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To what position are the CV / RV internally loaded? (RP)

CV = closed
RV = open

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What stops what from dripping constantly from the relief port during static / flow conditions?

Flow conditions = Supply pressure acting on a diaphragm w/in the RV
Static = closed CV + supply pressure

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Why should adequate clearance to ceilings and walls be provided around an RP?

for testing purposes
Facilitate removal of PRV + CV

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Why should an RP not be installed in a pit below ground?

Creates a cross connection if the atmospheric vent is submerged in ground water

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What is the exception of putting an RP below ground?

Semi - recessed pit w/ bore sighted daylight drain

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What precautions should be observed when an RP is located w/in a building?

Provide drainage to receive spillage from RV port

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When is a strainer not recommended to be installed upstream of an RP?

on a fire line backflow preventer
- Needs approval from AHJ or insurance underwriters

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True or False: RPs are normally installed horizontally.

True

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What can be installed upstream of an RP if the supply pressure is subjected to pressure fluctuations which result in periodic spilling from the relief port?

Soft seated check valve

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a DCVA / DCDA consists of?

2 indy acting, internally loaded CV
2 tightly closed shut off valves
4 test cocks

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What is the difference bn a DCVA and a DCDA?

Consists of everything a DCVA has plus another DCVA + water meter –> detects any leakage or unauthorized usage of water

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What are the hazards / hydraulics that a DCVA / DCDA protect against?

Hazards: minor, moderate, severe
Hydraulics: con’t pressure, back pressure, back siphonage

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When can a DCVA be installed on a pit below ground?

When the pit can be provided w/ adequate drainage to maintain a dry pit
- test cocks have to have water tight coverage / plugged

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What must be done to a DCVA if it is installed in an area prone to flooding?

A pressure vacuum breaker assembly (PVB) consists of?

internally loaded CV
internally loaded vacuum RV for the downstream side
Inlet / Outlet shut off valve
2 test cocks

To what position are the CV and vacuum RV internally loaded?

CV - closed RV - open

How does a spill resistance pressure vacuum breaker (SRPVB) differ from a PVB?

SRPVB has an additional internal spill - resistant membrane

What are the Hazards and Hydraulics that a PVB will protect against?

Hazards: minor, moderate, severe Hydraulics: con't pressure, back siphonage

A PVB must be installed a min of (what) inches above the highest downstream piping?

12" (300mm)

What is an option if occasional spitting from a PVB is objectionable?

Installing a SRPVB

What does an AVB consist of?

- Valve body containing a Vacuum RV (aka poppet) - Vacuum RV seat - CV seat - Atmospheric vent

What are the Hazards and Hydraulics that an AVB will protect against?

Hazards: minor, moderate, severe Hydraulics: back siphonage

What is the max duration that an AVB may be subjected to a con't pressure?

less than 12 hours

True or False: a shutoff valve used in conjunction w/ an AVB may be located upstream from the AVB.

True

How high above the highest downstream piping must an AVB be installed?

1" (25mm) Manufacturer's recommendation = 6" (150mm)

May an AVB be installed in a horizontal orientation?

No, vertically - needs to be in a visible location for maintenance

What does a hose connection vacuum breaker (HCVB) consist of?

- CV force loaded to a normally closed position - atmospheric vent

What does a hose connection dual check type vacuum breaker (HCDVB) consist of?

Everything a HCVB has plus a second (downstream) CV

What type(s) of backflow and hazards is the HCVB effective to protect against?

Hazards: minor, moderate (when paired with DCVA, RP or AG), Severe (when paired w/ RP or AG) Hydraulics: back siphonage

A HCDVB will protect against back siphonage and low head back pressure dt the terminal end of the hose being at an elevation equal to or less than?

3m (10')

What class of hazard is the HCDVB effective to protect against?

Minor

What kind of outlets are HCVB / HCDVB installed on?

Hose threaded outlets ex: hose bibs, service sinks + wall hydrants

Can a HCVB be subjected to a con't pressure?

What does a lab faucet vacuum breaker (LFVB) consist of?

- 2 indy acting CVs - normally closed position - auto venting to atmosphere - vacuum breaker

A LFVB shall be located on which side of the last control valve?

Discharge side

What does a dual check w/ atmospheric port (DCAP) consist of?

- 2 indy acting, internally loaded normally closed CV - Normally closed atmospheric port

True or False: The DCAP is designed for use under con't pressure

True

Is a DCAP allowed to be used as a replacement for an RP?

No - Does not protect against moderate or severe hazards

What does a dual check valve backflow preventer (DuC / DuCF) consist of?

- 2 indy acting CV force loaded to normally closed position - normally closed atmospheric port

What is the outcome if a carbon dioxide or carbonated water were to backflow into copper piping?

Can leach metals into drinking water supply Causes copper poisoning

The piping or fittings downstream of a DCAPC (Dual check w/ atmospheric port for carbonated water) shall not be made of?

Copper or copper alloy material

True or False: the DuC/DuCF has at atmospheric port.

True

What does a single check valve assembly for fire systems (SCVAF) consist of?

- 1 internally loaded CV - 2 tightly closing, resilient seated, shutoff valves - Test cocks

What does a barometric loop consist of?

pipe arrangement that uses the principle that a perfect vacuum can only lift water 10m (34') at atmospheric pressure

What do the initials IAPMO stand for?

International Association of Plumbing + mechanical Officials

Name 6 types of water - using equipment which have built in backflow preventers

1) clothes washing machines + dishwashers 2) Toilet or Urinals 3) Chemical or detergent dispensers 4) Beverage machines + dispensers 5) Ice Machines 6) Double wall heat exchangers w/ a visible means of leak detection