The Automatic Truth about Manual Wet Standpipes
Many in the fire protection industry, as well as the fire service, do not fully understand what a manual wet standpipe is and how it works. This blog will focus on the basic installation and testing requirements and shed some light on this rarely understood topic.
Defining Manual Wet Standpipes
First, let’s learn what a manual wet standpipe is. NFPA 25, The Standard for Inspection, Testing and Maintenance for Water-Based Fire Protection Systems, does not specifically define a manual wet standpipe. However, the standard breaks it into two definitions. First, a wet standpipe is defined in Section 220.127.116.11 and it states that it is a system that always contains water. A manual standpipe is defined in Section 18.104.22.168, and states that it is a system that relies exclusively on the fire department connection to supply the system demand.
NFPA 14, The Standard for the Installation of Standpipe and Hose Systems, defines a wet standpipe the same as NFPA 25, however, unlike NFPA 25, it specifically defines a manual wet standpipe. A manual wet standpipe is defined in Section 22.214.171.124of NFPA 14. It is a standpipe system that relies exclusively on the fire department to supply system demand and always contains water.
NFPA 14 (2019) Section 126.96.36.199 requires a sign at the fire department connection (FDC), stating the type of standpipe and if it is a manual standpipe, also it must indicate if it is a wet or dry standpipe. It must also indicate the inlet pumping pressure required to meet system demand if the pressure is greater than 150psi, in accordance with Section 188.8.131.52.2.1. Refer to the photo below for an example.
Because the system is a manual standpipe, it will never meet system demand or pressure without additional water supplies such as fire department pumper trucks. At acceptance of a manual wet standpipe system, the standard allows for available water supply, such as the fire hydrant, in addition to the fire department pumper to supply system demand. Figure A.11.5.2.(c) in NFPA 14 provides an example of how this works.
Once the system is installed and accepted, the adopted edition of NFPA 25 will determine if a manual wet standpipe system will require flow testing. The 2011 edition requires only automatic standpipes to be flow tested. The 2014 edition requires all Class I and III systems to be flow tested, this includes manual standpipe systems. The 2017, and all editions since, require only automatic standpipes to be flow tested. NFPA 25 does not change the flow test requirements for manual or automatic standpipes, it only states that the most remote outlet must flow 500 gpm and every additional standpipe must flow 250 gpm simultaneously until system demand is met.
System demand for a combination sprinkler and standpipe system is 1000 gpm, standpipe only (no sprinklers or partially sprinklered building) is 1250 gpm. System protected throughout by a 13R system (The installation of Sprinkler Systems in Low-Rise Residential Occupancies) is also 1250 gpm. For buildings with full sprinkler systems and standpipe with three standpipes, the most remote standpipe must flow 500 gpm while the other two must flow 250 gpm each until 1000 gpm is flowing simultaneously.
How do you flow test a manual standpipe once installed? There are a few options, such as using existing water supplies in addition to supplementary supplies. The supplementary supplies could be the fire department or a temporary fire pump.
From an inspection and testing standpoint, we must know the type of standpipe and how to test it accordingly. Unfortunately, in many cases the FDC is not labeled properly. Without proper documentation on site to verify the type of standpipe, the system will typically be tested as an automatic system. Again, if the system is manual and tested as an automatic, it will not meet the flow test requirements of NFPA 25. In accordance with the annex table for fire protection system inspection findings, this will result in a critical deficiency. In addition, standpipes are for fire department operations, properly identifying and maintaining standpipes is a critical requirement for life safety.
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