Chapter 4 - Backflow preventers Flashcards
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
What are the measurements of an air gap?
2x pipe diameter
min 1 “
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
Are approved air gaps required to be included in a yearly testing program?
Yes
Are air gaps usually accompanied by the installation of an RP for area isolation?
Yes
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
What does the “D” stand for in RPD?
Detector
What is the difference bn RP and RPD?
RPD has everything a RP has, plus additional RP / water meter in a bypass configuration
What are the hazards / hydraulics that an RP / RPD protects against?
Hazards: Minor, Moderate, Severe
Hydraulics: Con’t pressure, Back pressure, Back siphonage
To what position are the CV / RV internally loaded? (RP)
CV = closed
RV = open
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
Why should adequate clearance to ceilings and walls be provided around an RP?
- for testing purposes
- Facilitate removal of PRV + CV
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
What is the exception of putting an RP below ground?
Semi - recessed pit w/ bore sighted daylight drain
What precautions should be observed when an RP is located w/in a building?
Provide drainage to receive spillage from RV port
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
True or False: RPs are normally installed horizontally.
True
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
a DCVA / DCDA consists of?
- 2 indy acting, internally loaded CV
- 2 tightly closed shut off valves
- 4 test cocks
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
What are the hazards / hydraulics that a DCVA / DCDA protect against?
Hazards: minor, moderate, severe
Hydraulics: con’t pressure, back pressure, back siphonage
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
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?
No
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
