Where can I locate Pressure Reducing Valves (NFPA 13 & 20)? 2

[Jo9008]

NFPA 20 says I cant use a PRV after my pump discharge to limit system pressure. Well where does that "discharge" end? Can I put it at the the base of a riser? Does the riser need a check valve? Or can it only go after floor control valves?

 

[UFT12]

NFPA 20 Handbook, "It is important to note that the scope of NFPA 20 stops at the discharge control valve, and nothing in NFPA 20 prohibits the use of pressure-regulating devices downstream of the discharge isolation valve."

With that said, you will have to look at other standards downstream the control valve that govern the system to see what are the requirements about PRVs.

 

[PEDARRIN2]

It makes no sense to put a PRV in the immediate downstream piping of a fire pump - just specify a smaller HP pump for a lower pressure.

However, the typical place we use them is when we have a multistory building which requires 100 psig at the top of the standpipe but we also have sprinkler zones at lower floors. To not have to use valves/fittings rated for >175 psig, we will specify a PRV at the floor/zone control valve to lower the pressure. Also, some fire departments do not want excessive pressure at the 2.5" valve so means to reduce the pressure is specified.