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.