青云翻译

Roof drainage system + the total drainage capacity of the overflow is not less than 50 year return period rainfalls.

+ Roof rainwater drainage system overflow of total capacity of not less than of 50 return period rainfall.

Roofing rain water drainage system + overflow total flow capacity is not smaller than 50 year return period rain water quantities.

Roof rain water drainage system + overflow of total drainage capacity is not less than 50 return period the rainwater.

+ Roof rainwater drainage system overflow of total capacity of not less than of 50 return period rainfall.