In the Fire Service, we tend to find the easier way to complete a task and there’s nothing wrong with that. That mindset allows us to quickly come up with ways to overcome issues in emergency situations. We can find a way to complete any task with any given resources and every Firefighter will have a different and “better” way to do it. Pumping a fire is one of these tasks we have made easier through the years. Most departments will have a set pressure for most common lays, 150 psi. for the 1 ¾” preconnect, 90 psi. for the 2 ½”, etc. This works great for a quick room and contents fire or a car fire but what happens when we get something more complex. We need to get back to basics and pump for GPM.
We were all taught ways in Rookie School to estimate the needed GPM for a fire and we went over it again in Officer training. The NFA formula, [(length x width) ÷ 3] x percent of involvement, works great but we don’t always use it and if we do, we don’t apply it to pump operations or track it. We need to focus on deploying, charging, and pumping lines for GPM. It’s fine to have predetermined discharge rates for common lays, it makes initial operations faster, but let’s focus on the GPMs of the lines.
Creating a pump chart that has the friction loss already figured for lines of all lengths and diameters at varying GPMs is a great way to allow you to quickly figure the needed Pump Discharge Pressure for any lays you have down. Another great tool is an Operator’s Worksheet to track what lays you have down. There should be a spot for each discharge that allows you to capture the length, diameter, GPM, PDP, time pulled, any changes, and anything special such as wyed lines. It’s nice to also have spots to track intake pressures and engine information such as oil temp, fuel, etc. Using a sheet like this allows you to look back during an After Action Review to verify the needed fire flow. With this you can start finding trends and adjust your operations based on real world information gathered from your district.
As an Incident Commander it’s important to pull lines based on the needed GPM to control and extinguish the fire. When a line needs deployed radio the Operator with the additional lines GPM to verify it can be pumped. If the Operator is tracking the current GPM they can estimate the GPM remaining in the hydrant based on the 10/20/30 rule and radio back if the line can be pulled. As IC you have the ultimate call to pull the line if the Operator states the hydrant can’t support it, but this gives you a good picture of the current situation and allows you to adjust operations accordingly.
There are many benefits to focusing on GPM and it’s something we already know how to do, we just need to practice with it and use it.