sprinklernotes
Antifreeze Systems with Backflow Preventers
You asked the following question: “We have an NFPA 13 system that will be using
listed antifreeze for the entire structure. After the backflow preventer
(BFP), the riser assembly will be the typical vertical orientation. Does
Figure 7.6.3.3 require the components after the BFP to be in a horizontal
orientation?” In response to your question, we have reviewed NFPA 13, 2016
edition as the applicable standard. Our informal interpretation is the riser
is not required to be horizontal.
A primary function of Figure 7.6.3.3 is simple to show that the standard drop
loop required when using a check valve (with a 1/32-in hole) is not necessary
when the assembly includes a backflow preventer. The drop loop was to minimize
the migration of the antifreeze solution when pressure was relieved (due to
thermal expansion) through the hole in the check valve. When a BFP is used
there is no migration and pressure is relieved by the use of an expansion
chamber. As such, a drop loop is not needed. Although the orientation of the
assembly is irrelevant, some of the components must be located as indicated in
relation to the sprinklers. As common sense would dictate, the drain valve
must be located at a low point and the fill cup must be above the plane of the
sprinklers. Naturally, if a fill connection (pressure-driven) is used instead
of a fill cup, then its placement in reference to the sprinklers is irrelevant.
