Chlorine residual, chloramines and chlorine demand measurement context
Free chlorine is the hypochlorous acid and hypochlorite left in water after chlorination; total chlorine also includes combined chlorine, mainly the chloramines that form when chlorine reacts with ammonia. Systems that disinfect with chloramines follow total chlorine or monochloramine. Chlorine demand is the amount of chlorine the water uses up over a set contact time: the chlorine added minus the residual left. Residuals are expressed as mg/L chlorine (Cl2). Chlorine residual changes soon after sampling. Dissolved oxygen and inorganic tests
Define where the property is measured
Specify field or laboratory measurement, units and the sample state needed for the project. A delivered sample may not preserve the source-time condition for a changing property.
Include the complete project requirement
Provide the matrix, target analytes, required method, fraction, units and reporting limits. Include the permit or monitoring instructions where results will support a regulatory submission. Naming this method does not establish blanket compliance eligibility.
Resolve collection before sampling
Use the bottle, preservation and delivery instructions assigned to the agreed scope. Identify each location and collection time, and document any deviation. The final analytical plan must fit the submitted material and its intended use.
Related testing & guidance
Technical & service references
Vanguard service detailsSource review: November 8, 2026. The agreed method and project scope govern the testing.