How long will your water last? Enter the water on hand and the flow rate to get the run time — essential for tank water, tender/tanker shuttles, and rural water supply planning.
Duration is the water on hand divided by the flow rate. For sustained operations, your incoming supply (hydrant, relay, or tender shuttle) must match or exceed the flow rate, or the clock is running on your tank.
Run time is simply the available water divided by how fast you are flowing it:
To work the other way — how much water you need for a set time — multiply:
A 1000-gallon tank flowing a 150 gpm attack line with no incoming supply, counting every gallon in the tank (as the calculator above does):
That is why establishing a continuous water supply early is critical — a single tank empties fast at fireground flows.
The scenario: a 1,000-gallon tank supplying one 1¾" line at 150 GPM.
Not every gallon in a tank reaches the pump, so plan on usable water rather than the full tank: Duration = usable water ÷ total flow. Figuring ~90% of tank capacity is actually usable: 900 ÷ 150 = 6 minutes — a little under the 6.7 minutes the calculator gives for the full tank. Open a second identical line and it's 3 minutes.
Six minutes is enough to darken a room-and-contents fire — and nowhere near enough for anything bigger. That's the calculation behind the rule every engine company lives by: the attack starts on tank water, but the water supply plan starts before the attack does.
PumpForge models tank water, relay, and draft supply so operators learn to manage water before the tank runs dry — realistic panel, automatic scoring, after-action reports.
See the fire pump simulator →For training and estimation; always verify against your apparatus and SOPs. Related tools: required fire flow, pump discharge pressure, and foam concentrate. Water supply management is a core competency in NFPA 1002. Verify hydrant capacity before you rely on it with a fire hydrant flow test. When the water is farther away than one engine can move it, see relay pumping.