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Water Based Sprinkler Systems
2 major different types of water sprinkler
systems
Wet pipe system
Dry pipe system
Wet Pipe System
Water is in all piping
As sprinkler heads open, water is
discharged
Wet Pipe Clapper Valve
Dry Pipe System
Air is in system from above the clapper
valve to to sprinkler head.
As sprinkler heads open, air escapes
then water is discharged.
Dry Pipe Clapper Valve
Pre-action Systems
Sensors in the area of the fire are
activated.
The water valve is then open.
And water flows to the area.
Deluge System
All sprinklers are activated at once
when a detecting device is activated.
Typical Wet Pipe System
In a typical wet pipe system, water
enters the building at a determined
pressure.
Backflow Preventers
Backflow preventers are placed before the
riser.
If there are significant decreases in water
pressure, the backflow preventers prevent
water from being sucked out of the sprinkler
system.
These backflow preventers must be checked
by certified plumbers at least annually (EPA
requirements).
Back Flow Preventer
Sprinkler Riser
The water then flows to the riser.
At the riser, a series of valves and
gauges, maintain the water in the
system.
OS & Y Valve
Outside stem and yoke valve.
The water first passes through an
outside stem and yoke valve. (OS & Y
valve).
To close this valve, the handle must be
rotated out.
OS & Y Valve
OS & Y Valve
OS & Y Valve Example
Tamper Switches
In some instances, there are tamper
switches on these valves.
If they are turned, the monitoring
service will receive a trouble alarm.
This valve should be alarmed and
chained open.
Tamper Switches
Main Water Clapper
The water then enters the main section
of the riser.
There is a main water clapper that sits
at the base of the riser.
If there is major water pressure loss, the
water will stay in the sprinkler system.
Water Gauges
Water pressure gauges are found
above and below the water clapper.
This will alert the person to pressure
problems in the water lines.
In a wet pipe system, both pressure
gauges may read the same.
Check the design spcifications!!
Water Flow Alarm
These are found above the main
clapper.
If there is a flow of water, the alarms will
be activated.
2" Main Drain
A two inch pipe comes out of the main
riser area to a drain.
This two inch line is used for testing
purposes.
Closing the water valve above the 2
inch line then opening the 2 inch water
line tests water coming in from the
municipal service.
Riser
The next section of pipe is the riser pipe
itself.
The riser pipe goes up to the sprinkler
branch lines in the building.
Branch Lines
The branch lines are typically smaller
than the riser.
This decrease in the diameter of the
branch lines increase the pressure in
the lines.
Inspectors Test
Located at the furthest point from the
riser
Simulates the opening of one sprinkler
head
Wet Pipe Sprinkler System
Inspections
Inspector's test
2 inch main drain test
Water flow alarm test
Inspectors Test
Signifies that one sprinkler head at the
sprinkler head furthest from the riser
has been opened.
This verifies that adequate pressure and
flow can be achieved.
Water Flow Alarm
"Trip test“.
– At the inspector's test valve, open the inspectors
test valve.
– A slight decrease in pressure should be observed.
– The water flow alarm should be activated and the
fire department should receive a signal that the
fire alarm has been activated.
– There should be a short time delay from when the
water flows and the alarm is activated.
– The delay should not be any greater than 90
seconds.
– Close the inspectors valve and reset the system.
Two Inch Main Drain Test
– The purpose of the two inch drain is to determine
if there is adequate water supply to the system.
– Open the two inch drain fully, check and record
the water pressure.
– There should not be a significant drop in water
pressure when the two inch drain is open.
– If there is, there may be a blockage in the supply
line.
– Close the two inch drain and record the pressures.
– The pressure should return to approximately
normal.