Inflow & InfiltrationIntermediate 28 min read

Inflow & Infiltration: System Optimization

How Class 3 operators move from finding I&I to quantifying and ranking it — flow monitoring data analysis, rainfall-derived I&I (RDII), CCTV defect identification, rehabilitation prioritization, and the often-underestimated role of private lateral I&I.

Finding an I&I source is only half the job. A Class 3 operator is expected to help answer the harder questions a utility actually has to make decisions on: how much I&I is entering the system, which basins are contributing the most relative to their size, and where rehabilitation dollars should go first. This guide covers the quantification methods, defect-identification tools, and prioritization logic that turn raw flow data into a rehabilitation plan — plus the private lateral problem that many I&I programs underestimate.

Quantifying I&I: Flow Monitoring Data Analysis

Once a utility has continuous flow monitoring data from a basin, the next step is separating that flow into its components. The U.S. EPA's Guide for Estimating Infiltration and Inflow (New England, June 2014) defines a standard set of terms used to do this:

Base Sanitary Flow (BSF) — the portion of was

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