In the previous chapters, it has been assumed that fresh resources can always ful‘ll the needs for various sinks in a resource conservation network (RCN). However, there are cases where this assumption does not hold. For instance, water pretreatment units are always used in the process plant to produce dematerialized water (e.g., for boiler feed water, specialty chemical production) or ultrapure water (e.g., semiconductor manufacturing). In most cases, the pretreatment units are normally used for purifying fresh resources before they are sent to the process sinks, which require stringent quality. In this chapter, the two-step insight-based pinch analysis technique is used to synthesize a pretreatment network. In the ‘rst step, the material recovery pinch diagram introduced in Chapter 3 is extended as the pretreatment pinch diagram (PPD), which is used for targeting the minimum treatment ¤owrate for a pretreatment network. In step two, the design of a pretreatment network with nearest neighbor algorithm introduced in Chapter 7 is also discussed.