When the building is fully protected by one or more automatic water fire extinguishing systems, such as automatic sprinkler system, water spray fire extinguishing system, foam fire extinguishing system or fixed fire monitor fire extinguishing system, when the height of high-rise building is less than 50m and the design flow of indoor fire hydrant exceeds 20L/s, the design flow of indoor fire hydrant can be reduced by 5l/s according to Table 4-3; The design flow of indoor fire hydrants in multi-storey buildings can be reduced by 50%, but it should not be less than10l/s.

Figure 4-5 1 is an example of the decrease of indoor fire hydrant flow.

Figure 4-5 1 Example of flow reduction of indoor fire hydrants

(a) the design flow of fire hydrant can be reduced; (b) The design flow of fire hydrants should not be reduced.

As can be seen from Figure 4-5 1, the flow of fire hydrants in the garage is no longer reduced; Only when one or more automatic fire extinguishing systems are fully protected can they be reduced.