Chlorine Residual Decay (First-Order)

First-order residual C(t) = C0 x exp(-k t), time to a target residual, and an optional booster distance. Per EPA 815-R-02-020 and AWWA M14; 40 CFR 141.74 governs the extremity residual.

Run the calculator

Formula and source

First-order decay C(t) = C0 x exp(-k x t). Time to target = ln(C0 / target) / k. Booster distance = distribution velocity x time-to-target (when a velocity is entered).

EPA 815-R-02-020 (Effects of Water Age on Distribution System Water Quality); AWWA M14.

Audience

This tile is built for water operators and the adjacent professions in the Water and Wastewater Operations group. The interactive calculator runs entirely in your browser. No account, no fee, no advertising, no tracking.

Related tools

Posture

Rough Logic answers the math question the working professional asks on the job. The site is a calm, fast, ad-free, account-free, ever-free reference. It does not interpret code. It does not replace the licensed professional. It does not store your inputs. The Authority Having Jurisdiction governs all installations and inspections.