Filling and Pumping at the Same Time

A frequently asked question concerning Firovac is "On your vac/pumpers is it possible to fill the tank at a draft site while at the same time as pumping into another truck?"

The answer is: We do not set our units up to do that for the following reason,

Although it could possibly work for a short period of time, eventually the vacuum pump will overcome the fire pump and it will cavitate the fire pump. A fire pump functions at 15-16 inches of mercury and the vacuum pump goes up to 25-27 inches of mercury. Cavitation of a fire pump will destroy the impeller.

Furthermore, a more efficient way to supply water is to discharge it into a drop tank from which the pumper can fill. Pumping directly into another truck provides no water reserve beyond the booster tank. A drop tank is worth another tank in the system as it extends the water reserve.

The picture below shows Firovac drafting from a creek and discharging into a drop tank. The pumper then drafts from the drop tank to fight the fire.

Comments

A couple of years ago, we participated in a GBW class and used their “suck and dump” method to supply a pumper at a fill site for tankers. The pumper could not draft from the water source but our vacuum tanker had no problem getting water. GBW had us only use the top 50% of the tank. It made sense to use this method fairly quickly. The air movement of the vacuum pump is most efficient when there is less air to move. By only using the last 50% of the empty tank we were using the vacuum pump at its most efficiency. The fill site was able to easily supply a 1000 GPM fill site operation from an otherwise unusable site.