Engine Company Operations — Fireground Flow

Generally speaking, fire departments should achieve 150gpms for 1.75” hose, 210gpms for 2” hose, and 250gpms for 2.5” hose. These should be the absolute minimum standard flows for any fire department. The key elements are the nozzle, hose and pump. All of which should be flow tested annually.

Nozzle selection is critical. Think about the nozzles that your department currently utilizes. How were these nozzles selected? Were they selected because their performance matched what your department was trying to achieve or were they chosen because a sales rep said it was the nozzle to buy. There are a multitude of different nozzles on the market today.  When it comes to selecting the right nozzle, application is everything.  What is the intended use for the nozzle? What is the flow rating for the nozzle? What type of stream will the nozzle produce? There are numerous opinions about which nozzles are the best; manufacturer, fog or smoothbore. I feel that simplicity is best. Nozzles with the least amount of moving parts typically will give you the least amount of problems. Again, nozzles should be flow tested each year to ensure operational accuracy. 

Whether your department utilizes smoothbore or fog, make sure that the hose construction matches the nozzle type. Hose construction can have a direct effect on flow and the ability of the firefighter to manage the line. There has been a trend to move to low pressure nozzles (75 and 50psi) however, a lot of departments are using hose with low pressure nozzles that was constructed for nozzles with higher operating pressures (100psi). This mismatch causes the line to kink specifically near the nozzle, creates nozzle whip while flowing and can make the hose difficult to manage.

Hose and nozzle packages are simply a recipe. The department should attempt to achieve a hose and nozzle combination that will give a minimum flow of 150gpms, a nozzle reaction less than 71 pounds, and a pump discharge pressure in the 100-140 psi range. The hose and nozzle is the firefighter’s weapon when going to battle. As a police officer understands the ballistics of their ammunition for their gun, firefighters should know the performance of their hose and nozzle. This equips the firefighter with knowledge so that they confidently choose which hose and nozzle package to utilize at a given fire, which in turn allows for an aggressive fire attack.

One element of fireground flow that is often overlooked is the pump on the apparatus. The piping of the pump can increase friction loss as much as 10 to 15 psi, which affects flow. The piping is plumbed to work within the body based on desired discharge locations and body style. Another concern are gauges. Are they accurate? Where do the gauges measure the pressure in the piping? Pumps are service tested every year, but are they tested when measuring flow for the fireground?

In order to sustain the desired fireground flow, a positive water supply should be established. A water supply is just as important to sustain the desired fireground flow. The key to having a positive water supply is in pre-planning. The department must get out and address those areas where they can expect difficulties and how to deal with them. The water supply must meet — preferably exceed — the fireground demand. If the water supply fails to meet the fireground demand, everyone loses! The water supply must be established quickly. Firefighters must know all the options on where the water is coming from. Hydrants are usually quick, reliable and require minimal personnel to establish. Firefighters should make sure that the hydrant is flushed to remove debris and to ensure that the hydrant has water. Drop tank operations are personnel driven to set up and can be time consuming if firefighters are not trained in setting one up. When conducting a drop tank operation, success is based upon the ability of quick dump and quick fill. Remember to try to avoid routes or tank placement that requires apparatus to back up. Lastly, when laying supply lines firefighters should work to avoid kinks. It is ingrained in firefighters to chase kinks on the attack line because it will affect flow out of the nozzle. The same can be said for the supply line. If the supply line has a kink, it will directly affect the fireground operation by reducing the available flow on the intake side.

It is a known fact the fireground is dynamic and every situation is different. For the engine company the ability to match the fireground flow to address the fire is a necessity. The ability to understand how the different components work together to achieve the proper flow is critical to winning on the fireground.