Summary of Diameters of Various Firefighting Pipes

01. DN65:
1. When commercial facilities such as restaurants and shops are connected through a covered pedestrian street, and the buildings on both sides of the pedestrian street need to use the pedestrian street for safe evacuation, DN65 fire hydrants should be installed every 30m outside the shops of the buildings on both sides of the pedestrian street.
2. If it is difficult to install an indoor fire hydrant system for residential buildings with a building height ≤27m, only dry fire standpipes and DN65 indoor fire hydrants without fire hydrant boxes can be installed.
3. Indoor fire hydrants should use DN65 fire hydrants.
4. A DN65 water test pipe should be installed on the outlet pipe of each fire water pump.

02. DN75:
1. The diameter of the drainage riser at the end water testing device of automatic water fire extinguishing systems such as automatic sprinkler systems should not be less than DN75.
2. The diameter of the drainage standpipe at the end water testing device of automatic water fire extinguishing systems such as automatic sprinkler systems should be determined based on the discharge capacity of the end water testing device, and should not be less than DN75.

03. DN100：
1. The water inlet pipe of the fire pool should not be smaller than DN100.
2. The diameter of the overflow pipe of the high-level fire water tank should not be less than DN100.
3. The diameter of the outlet pipe of the high-level fire water tank should not be less than DN100.
4. When the urban population is less than 25,000, the diameter of the annular pipe network connected to the municipal pipe network should not be less than DN100, and the diameter of the branch pipe network should not be less than DN150.
5. The diameter of outdoor fire water supply network pipes should not be less than DN100.
6. The diameter of the indoor fire hydrant standpipe should not be less than DN100.
7. The drainage riser at the alarm valve should be DN100.
8. The diameter of the drainage pipe for the pressure test at the pressure-reducing valve should be determined based on the flow rate of the pressure-reducing valve, but should not be less than DN100.

04. DN150：
1. When the suction pipe of the fire pump passes through the fire pool, a flexible casing should be used; when a rigid waterproof casing is used, a flexible joint should be set on the water pump suction pipe, and the pipe diameter should not be larger than DN150.
2. When the municipal water supply pipe network is equipped with a municipal fire hydrant, the municipal fire hydrant should use an outdoor fire hydrant with a diameter of DN150.

05. DN200:
1. The diameter of the municipal water supply pipe connected to the fire water should not be less than DN200.
2. The pipe diameter of the annular water supply pipe network connected to the municipal fire hydrant should not be less than DN150, and the pipe diameter of the branch pipe network should not be less than DN200.

06. Others:
1. For the gas supply pipelines of dry systems and pre-action systems, when steel pipes are used, the pipe diameter should not be less than 15mm; when copper pipes are used, the pipe diameter should not be less than 10mm.
2. In residential areas, it is advisable to reserve a connection for a DN15 fire hose or light water hose on the domestic water supply pipe.
3. The working pressure of the hydraulic alarm bell should not be less than 0.05MPa. The diameter of the pipe connected to the alarm valve should be 20mm, and the total length should not be greater than 20m.
4. The connecting pipe diameter of the short riser and the terminal water testing device should not be less than 25mm.
5. An end water testing device should be installed at the sprinkler head at the most unfavorable point controlled by each alarm valve group, and water testing valves with a diameter of 25mm should be installed in other fire protection zones and floors.
6. The diameter of the water inlet pipe of the high-level fire water tank should not be less than DN32, and the water inlet pipe should be equipped with a liquid level valve or a float valve.
7. The single-hole diameter of the nozzle in the dry powder fire extinguishing system shall not be less than 6mm.
8. Pressure gauges should be installed on the suction pipe and outlet pipe of the fire water pump. The diameter of the pressure gauge should not be less than 100mm. Pipes with a diameter of not less than 6mm should be used to connect the inlet and outlet pipes of the fire water pump and shut-off valves should be installed.
9. The fire pump suction pipe can be equipped with a pipe filter. The water passing area of the pipe filter should be greater than 4 times the water passing area of the pipe, and the pore size should not be less than 3mm.
10. The indoor fire hydrant should be equipped with a lined fire hose with a nominal diameter of 65, and the length should not exceed 25.0m; the fire hose reel should be equipped with a fire hose with an inner diameter of not less than ф19, and its length should be 30.0m; the light hose should be A lined fire hose with a nominal diameter of 25 mm should be equipped, and the length should be 30.0m; a fire hose with an equivalent nozzle diameter of 16mm or 19mm should be equipped, but when the design flow rate of the fire hydrant is 2.5L/s, it should be equipped with an equivalent nozzle diameter of 11mm or 13mm Fire water guns; fire hose reels and portable water hoses should be equipped with fire water guns with an equivalent nozzle diameter of 6mm.