Dry pipe systems – Potter Releasing Systems User Manual
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Dry Pipe Systems
Dry pipe systems are usually installed in unheated buildings or where there is the danger of sprinkler pipes
freezing. They have pressurized air in the sprinkler piping, this allows for supervision of the system and
prevents water from entering the pipes. The dry pipe valve and associated equipment Shall be protected in
accordance with NFPA13 2010, 7.2.5.
This type of system uses a dry pipe valve which has an intermediate chamber or alarm port. Under normal
conditions, this section of piping has no water or pressure in it. A pressure type flow switch would be installed
on the alarm port, this could also be connected to a water motor gong on the outside of the building. Waterflow
switches on dry systems do not need retards as there should not be any water surges.
When a sprinkler head opens due to fire, the air pressure is released from the system, this allows the water
supply to open the dry pipe valve and enter the system piping. When the clapper of the dry pipe valve opens,
it exposes the alarm port to the incoming water supply. The pressure type flow switch senses this increase in
pressure and sends an alarm signal.
Dry pipe systems should also have a supervisory pressure switch installed to monitor the system air pressure.
This switch should be adjusted to send a low air signal when the system pressure drops 10 psi below normal.
This will prevent accidental tripping of the dry pipe valve due to low air pressure from a compressor failure.
They should also be monitored for high air pressure as too much pressure will delay the time it takes to bleed
enough pressure off the system to allow the water pressure to open the dry pipe valve.
Notes: All water control valves shall be supervised per NFPA 13 2010 8.16.1.1.2.1.
The room temperature where the dry pipe valve is located should be monitored to Prevent the valve
from freezing.
A bleeder valve and pressure gauge should be installed in line with the air supervisory switch for
test purposes.
A WCS (Water Column Switch) can be used to comply with NFPA13 2010, 7.2.5.4.1