At the Class 4 level, storage isn't just something you monitor — it's something you have to be able to size, and something you have to be able to prove is doing its regulatory job. This guide covers the two calculation frameworks that separate a top-tier distribution operator from everyone below them: how much storage volume a system actually needs, and how a clear well's disinfection contact time is verified against the Surface Water Treatment Rule.
Storage Volume Calculations
Total required distribution storage is generally understood as the sum of three components, each covered earlier in this course as a concept — here we quantify them:
Vtotal=Vequalization+Vfire+Vemergency Fire Flow Storage
Fire flow storage is the most straightforward to calculate: it's simply the required fire flow rate multiplied by the duration that flow must be sustained.
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