Properties Of Water & Backflow Flashcards
Fire needs how much oxygen to burn
15%
Water to steam expands how much
1700 times out of
How does a standard sprinkler suppress the fire
Soaks/removes fuel
Heat is measured in
BTU’s (British thermal units)
Water is composed of 2 gases which are
Hydrogen and Oxygen
H2O broken down means
2 parts hydrogen, 1 part oxygen
Liquid nitrogen in sprinklers is used too
Create ice plugs
Potable means
Fit for human consumption
What prevents contamination to supply
Backflow
Hardness in water is due too
Magnesium or calcium
Hardness in water is measured in
PPM or GPG
(parts per million)
(Grains per gallon)
Hydrogen sulphide causes
Odours
Iron or magnesium causes
Rust or stains
Turbidity causes
Cloudiness
Bacteria in water causes
Contamination
Specific gravity of water is
1
Specific gravity less then 1 means
It will float
Specific gravity of more then 1 means
It will sink
Atmospheric pressure is
14.7 psia
Liquid to a gas temp
100C or 212F
Freezing point of water
0C or 32F
Water is most dense at
4C or 39F
When pressure increases, what happens to the boiling point
Also increases
Latent heat of fusion is
Water Turing into ice
Latent heat of vaporization is
Liquid to a gas
1Ft cubed of water weighs
62.4lbs
1 imperial gallon weighs
10lbs
How many imperial gallons are in 1Ft cubed of water
6.24 gal
1 imperial gallon to ounces is
160 ounces
1 US gal to ounces is
128 ounces
1 cubic inch of water weighs
0.036lbs
US gal to Imp gal conversion
x 0.833333
Imp gal to US gal conversion
x1.2
Back pressure with backflows is when
Reverse in normal direction of flow, caused by system pressure being greater then that in supply line
Back siphonage with back flows is
Reversal in normal direction of flow in the pipe line due to negative pressure (vacuum) in the supply line
Strainers in back flows for fire protection should be eliminated because
They cause restriction/could plug up with debris
Control valves on back flows are generally
OS&Y or butterfly (must be indicating)
Relief valve on back flow will operate within
2-6 psi increase in intermediate zone
(All are 2 psi minimum)
2 kinds of anti freeze that can be used in sprinkler systems are
Glycerine or Propylene Glycol
Backflows cannot be altered without
Contacting manufacturer
Intermediate zone is also referred to as
Reduced pressure zone
Intermediate zone is equipped with
Atmospheric vent
Water in the intermediate zone during normal flow is how much lower then supply
5-11psi
What is the pressure inside the Intermediate zone during a static situation
5-8 psi lower then supply
The relief valve on an RPZ is held closed by
Supply pressure
Relief valve causes what kind of “trouble signal”
Visual
What installation feature must you check with the manufacturer about before install
Installing vertical
The backflow should be installed
In an accessible location for testing and servicing
The discharge line should never be
Hard piped to any drain
Relief valve discharge line should be
1 foot above the floor
Bypass line on Backflow is made up of
Water metre, control valve, check valve
Backflows require internal inspection every
5 years
back flow testing (flow test/performance test) how often
Annually
RPZ should have a visual inspection done how often to see if relief is discharging
Weekly
Fire department connection height
Not less then 18 inches, no more then 4 feet above the level of grade
Buildings that do not require an FDC
-Remote areas
-Large capacity deluge systems exceeding pumping capacity of FD
- single story buildings not exceeding 2000sqft
The check valves are spring loaded to hold
Minimum of 1 psi in the direction of flow
If the back flow has a meter, what must be done
Main check springs must be increased so that they’re greater then the metered bypass to ensure low volume flows will be recorded
What must the meter connection have on the backflow
Double check valve assembly
How many test cocks are there for testing a backflow
4
What backflow is preferred in he sprinkler industry
Double checck
Pressure loss in system from using a double check
4-6psi
RPZ backflow pressure loss to system
10-20psi
Backflow preventers should be installed about
Waist high
Fire pumps must be how far from back flows with OS&Y valves
10x pipe diameter
Fire pumps must be how far from back flows with butterfly valves
50 feet
Test to measure hardness of water
Mix soap in water, more bubbles more hard water is
When water freezes how much does it expand
10%
Water vapour is heavier then
Air and oxygen
Hazard classes for backflows are
Low
Moderate
High
Lethal
Which hazard is sprinkler water considered
Low hazard
What hazard is Antifreeze or foam considered to be
High
Example of lethal substance that backflow need to protect against
Radioactive or raw sewage
Backflow kind for low hazard class
Double check valve assembly
Backflow for moderate to high
Reduced pressure zone assembly
Lethal hazard class uses what kind of backflow
Air gap
Air gap must be a minimum of
1”, and 2x the diameter of the outlet
Spring tension on relief valve contributes how much pressure
3psi
DCVA #1 check must hold a minimum of
1psi in the direction of flow
When a backflow is installed, how often shall a main drain flow test be done
Quarterly
Typically, how many GPM can each 2-1/2” outlet produce
250 gal
When water is confined to a vacuum, how low can it boil
16C or 60F
How many BTU’s to create steam
970.3
BTU loss to create ice
134.4
Water supply test for design purposes is good for
12 months
Why is a 2-1/2” outlet preferred for hydrant flow testing over 4” outlet
2-1/2” provides more accurate reading
