Because dry pipe sprinkler systems are in-
stalled in areas where temperatures are expected
to drop below freezing, all parts of the system
must be airtight and kept free of water. Complete
drainage is essential.
Each fall, before freezing season comes, check
the pitch of all piping carefully using a spurt level
to detect dips and small pockets in the lines. Check
. broken, loose, or missing hangers; and
. water in low point drains.
Check air and water pressures weekly. If air
pressure losses exceed 10 psi, check the entire
system for tightness and eliminate air leaks.
Principal checking methods are as follows:
. Put a strong smelling oil, such as oil of
peppermint, into the air supply. This will produce
a strong odor at the point of leakage.
. Paint fittings with a soapy water solution
and watch for bubbles.
Check the temperature of valve enclosure and
maintain a temperature above 42°F.
Make certain that the valve between the inter-
mediate chamber and the alarm devices is open
on dry pipe valves.
Check drip valves at intermediate chambers,
making certain that clappers or balls are in a posi-
tion to allow drainage. This is done by lifting push
rods or by inserting a pencil in the opening. Water
leakage through this valve is an indication that
the water clapper is not holding tightly to the seat.
Check the air pressure. The air pressure
versus water pressure for differential dry pipe
valves should be as outlined in table 8-3 unless
otherwise specified by the manufacturers
operating instructions. Certain mechanical dry
pipe valves are designed to trip at a fixed pressure
of 10 to 15 psi. Maintain 30 psi air pressure on
Basic inspections for accelerators and ex-
hausters include the following:
. Check air pressure. The system and the
quick-opening device air pressure should be the
. Relieve excess pressure in the quick-
opening device by opening bleeder valves or
loosening air gauges.
If the system pressure is high, relieve the
excess pressure through the priming water test
valve. Close the valve as soon as pressures
balance. To avoid the possibility of tripping the
dry pipe valve, do not open the priming test valve
more than one turn and keep the valve to the
quick-opening device closed while the priming test
valve is open.
To make sure that dry pipe valves will operate
effectively in fire situations, they should be
trip-tested annually as follows:
1. Close the main control valve.
2. Open the 2-inch drain.
3. Open the main control valve until 5 psi
pressure shows on the water gauge.
4. Close the 2-inch drain valve slowly.
5. Open the inspectors test connection of the
system. Where there is no test connection, use the
most remote low point drain.
6. As soon as the dry pipe valve trips, close
the main control valve and open the 2-inch drain.
This is particularly important in permanently cold
7. Record initial air and water pressures, air
pressure at the trip point, and time required for
8. Examine and clean the dry pipe valve in-
terior. Replace facings and gaskets if needed.
9. Reset the dry pipe valve and the open con-
10. When a dry pipe valve fails to trip or when
a clapper fails to latch in the open position, notify
the person responsible for fire protection so that
a qualified sprinkler contractor may be contacted.
To test dry pipe valves you should do the
1. Close the main control valve and open the
2-inch drain valve and low point drain valves.
Table 8-3.Differential Dry Pipe Valve Air Pressure