Lack of water on the fire is a fire ground problem that seldom stands alone. When water is not being applied to the fire at the proper rate we can all agree that things get worse on the fire ground. When we look at fires where maydays or firefighter fatalities occurred we can often find reference to water loss or water problems. One such fire is the one Meridian Plaza fire which occurred in Philadelphia PA on February 23, 1991. This fire took the lives of three Philadelphia Firefighters. One (of several) issues that plagued firefighters at this fire was improperly set pressure reducing valves. These valves were set 
to allow 60 psi discharge pressure which was inadequate to operate the fire department's 1 3/4" hoselines and combination nozzles.
Pressure reducing valves are found on many standpipe systems and there are dozens of types of these valves. This blog post will show only a few so be sure to familiarize yourself with the ones found in your response area. Pressure reducing valves are designed to regulate the pressure at a given standpipe outlet. Pressures can be very high when dealing with fire pumps or gravity tanks. These valves are intended to prevent over pressurization of components after the valve. By reducing pressure flow is also reduced.
The best and easiest way to deal with a pressure reducing valve is to remove it completely. One style of pressure reducing valve threads onto the standpipe outlet. When this type of valve is found, remove it with a spanner or pipe wrench and proceed as normal. If the valve can not be removed you may have to go to the floor two floors below the fire and hook up there. If you are unable to remove any of the pressure reducing valves, ensure the valve is in the full open position and proceed with caution.
Some standpipe outlet valves have a pressure reducing device built into
them. Some of them can be adjusted with a screwdriver or allen wrench and others require disassembly of the valve and special tools. These are the pressure reducing valves that firefighters must be intimately acquainted with before the fire to ensure a successful operation.
Once we remove the pressure reducing valve we can control the pressure ourselves using the outlet valve and our inline pressure gauge.
Fantastic article. I am a fire sprinkler system designer/sprinkler fitter. I am also a former fire fighter. I have experience from both sides of these. Some, are even set at the factory. There are also pressure RESTRICTING valves that can serve a smilar purpose. With those come the same issues. Most are factory set to the designers spec, typically in a highrise with a pump. The residual (flowing) pressure will vary from floor to floor with it possibly decreasing as elevation increases (on q fire pump supplied system, but opposition for roof mounted gravity tank fed systems. The problem comes when the contractor is NOT using factory set devices and instead using field adjustable devices and fitters, not properly educated, setting them.
Thanks for posting this article.