of appliance restrictions. A 1,250-gpm master stream appliance has
a maximum allowed inlet pressure to the device of 200 per square
inch (psi), and based on the 1,250-gpm flow with a 100-psi nozzle,
pressure with a combination nozzle can only flow up to 631 pounds
nozzle reaction. In my testing, I have found that a 1,250 appliance
cannot reach 1,250 with the two-inch tip because of the nozzle reaction limitations. So, with that being said, either use a combination
nozzle for 1,250 gpm or set the goal for a fixed master stream with
the two-inch smooth bore tip for 1,000 gpm.
Here is another example of a maximum flow operation from
a single unit. The unit is a 2,000-gpm elevated platform with
a pump. Department standard operating procedures require a
2,000-gpm flow, so here is the evolution that will produce it efficiently. The quint gets the initial water supply with five-inch hose
from the closest hydrant. Unless the fireground area is already
being tapped by multiple hydrant use, or if it’s known that the
hydrant is weak, I don’t see a need to make this line a relay pump
operation; however, it would not be wrong to set it up as one.
Most hydrants cannot supply 2,000 gpm, but even if a hydrant
can, one of the issues that will be encountered with this operation
is an extremely high revolution per minute (rpm) from the engine
on the quint. What I recommend is to automatically lay a second
five-inch supply line back to a hydrant and set up for a relay/
tandem pump operation, which will bring in the extra water if
needed and will assist the engine of the quint by lowering its rpm
because of the pressure being brought in from the relay.
Whether a high-flow handline or master stream is going to be
placed into service, it needs to hit the fire. I know you are thinking, does this guy think we are stupid? Not at all. What I mean
is, move the stream around to hit as much fire as you can from
your location. So often I see that when a big stream is aimed into
a fire, it looks like a big drill trying to drill a hole. It doesn’t move.
It almost seems like crews are trying to fill the building up with
water from that point.
WATER SUPPLY EVOLUTIONS
When a multiple master stream operation is going to be put
into service to fight a sustained fire, this means that you have
to have the water supply to deliver this flow. If the water is
not available from the closest hydrants from the initial supply
line, then another engine needs to reverse out to a more distant
hydrant that is hopefully on another loop and relay pump. This
is something we used to do all the time before LDH. Big water
meant putting pumps on hydrants to pump to the engines that
were delivering the water. LDH has made a big change in water
delivery. However, the real magic in the hose realistically is for
Left: A 2,000-gpm stream. Right: This is a tandem pump operation. Notice the engine pumping in tandem 300 feet from the quint.
Left: Every apparatus should have at least one designated handline that can be used for a large flow operation, whether it’s preconnected or simply stored in the
hosebed. Right: An engine can lay a dry line and only charge it if needed.