This manual provides guidance and criteria for the design of small water supply, treatment, and distribution systems. For the purpose of this manual, small water systems shall be those having average daily design flow rates of 380 000 liters per day (l/d) (100 000 gallons per day (gpd)) or less. However, the use of the term small is arbitrary, there being no consensus in the water supply literature with respect to its meaning. Regulations regarding the acceptability of a water source, degree of treatment required, and the monitoring requirements are not based on flow rates, but rather on a water system classification relating to the number of people served and for what period of time. Figure 1-1 provides a flowchart for system classification. Refer to Chapter 3, paragraph 3-4b for the appropriate nomenclature.