水在配水系统中的停留时间（DS）是确定反应程度的一个重要因素。例如，随着停留时间的增加，消毒剂残留量减少，消毒副产物增加。消毒剂残留的损失会导致严重的细菌再生问题。虽然水设施人员越来越熟悉化学示踪剂研究，但尚未采用一种方法对DS产生的数据进行定量分析。另一种方法是通过水力建模计算水龄，但这需要开发网络模型及其校准。此外，网络骨架化的程度可能会限制其用于估算未包含在模型中的较小管道中的水龄的实用性。 本研究提出了一种计算平均成分停留时间（MCRT）的方法；该成分是一种保守的化学示踪剂。该方法已应用于北卡罗来纳州达勒姆市的DS，其中包括两个水处理厂（WTP），使分析更加复杂。开发了一项独特的示踪剂研究，以同时确定每个采样站每个WTP对流量的贡献百分比和MCRT的流量加权平均值。这涉及一个水处理厂的混凝剂切换，以及氟饲料浓度向另一个的变化。包括4个参考文献、表格和图表。

The residence time of water in the distribution system (DS) is an important factor in determination of the extent of reactions. For example, disinfectant residual decreases and disinfection byproducts increase with increasing residence time. Loss of disinfectant residual can lead to serious bacterial regrowth problems. While chemical tracer studies are becoming more familiar to water utility personnel, a methodology has not been adopted for quantitative analysis of the resulting data from the DS. The alternative is water age calculations from hydraulic modeling but this requires development of the network model and its calibration. Moreover, the extent of skeletonization of the network may limit its utility for estimating water age in smaller pipes that are not included in the model. This study presents a method to calculate a mean constituent residence time (MCRT); the constituent is a conservative chemical tracer. The method is applied in the DS of Durham, North Carolina where the analysis was made more complex by inclusion of two water treatment plants (WTPs). A unique tracer study was developed todetermine simultaneously the percent contribution to flow from each WTP at each sampling station and the flowrate weighted average of the MCRT. This involved a switch in coagulants at one WTP and a change in fluoride feed concentration to the other. Includes 4 references, tables, figures.