The amount of organic, inorganic, or total carbon in water or soil samples is measured by a combined lab water system with a built-in TOC monitor. Because TOC is a crucial indicator of disinfection by-products, drinking water facilities are required by the by-product regulation to assess TOC removal. The total organic carbon (TOC) content of the source rock is measured as a weight percentage. A combined lab water system with a built-in TOC monitor serves as a stand-in for the total amount of organic matter in the sediment and is a measure of source richness in terms of the potential hydrocarbon production of the sediment.