Fire Water Reserve (RTI)
Calculate the fire water reserve volume, V = flow × time ÷ 1000, multiplying the system's required flow (L/min) by the required autonomy time (min) and converting to cubic metres. The result, in m³, is the water volume the tank must keep reserved exclusively for firefighting — sized to feed hydrants and/or sprinklers for the minimum time set by codes (typically 30 to 60 min, depending on risk). It is a central calculation in building firefighting installation design. Enter the flow and the autonomy time.
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Fire water reserve (RTI)
The fire water reserve (RTI) is the volume of water that a building tank must keep permanently reserved and untouched for firefighting — held apart from the domestic supply (in practice this is secured by setting the fire riser outlet lower than the domestic one). Its calculation is direct: V = flow × time ÷ 1000, the flow rate required by the system (L/min) multiplied by the required run time (min), converted to m³. The logic is to guarantee that hydrants and/or sprinklers have enough water to operate for the minimum period in which the fire is expected to be brought under control, or until the fire brigade arrives and takes over — typically 30 to 60 minutes, depending on the occupancy, the floor area and the risk class set by the applicable Instrução Técnica (the state fire brigade technical instruction). The design flow, in turn, follows from the type of system: the number of hydrants operating at the same time, or the sprinkler design-area flow plus the hose stream allowance. Sizing the RTI means balancing safety against cost: larger reserves buy more autonomy, but they demand bigger tanks and heavier supporting structure. Enter the flow rate and the run time.
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The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.