sprinklernotes Inside Hose Allowance for Combined Standpipes
You asked the following questions: “In a combined sprinkler/standpipe riser, are you required to include the hose connection demand in the sprinkler calculation?” In response to your question, we have reviewed the 2016 editions of NFPA 13 and NFPA 14 as the applicable standard. Our informal interpretation is no, the two systems, despite having a common riser, are treated as two independent systems. Section 11.1.6.3.1 explicitly tells us that we do not have to include any inside hose demand in our sprinkler calculations when the system is a combined sprinkler/standpipe system. Additionally, section 11.1.6.4 says to calculate the two systems separately. This is additionally stated in A.11.1.6.2. Regarding section 7.10.1.3.1.1 of NFPA 14, there could be an instance where the fire sprinkler demand could exceed the flow rates of the standpipe system. It is rare but one instance that occurred in my plan review days was a healthcare research building where the laboratory had a density of 0.2 gpm/sq. ft. over 1,500 sq. ft. where the quick-response reduction was not allowed. The water flow demand exceeded that of the standpipe system riser of 250 gpm. The sprinkler flow was used in lieu of the standpipe demand. For that instance, let's say the sprinkler demand was 390 gpm (0.2 gpm/sq. ft. X 1,500 sq. ft. plus an additional overage of 90 gpm). That exceeded the flow of 250 gpm for that standpipe riser and the higher flow was used.
