Various methods for testing spiral wound modules by thermal imaging are described. In a preferred embodiment, the method(s) includes flowing a gas between a scroll face and permeate collection tube of a spiral wound module and detecting temperature differences on the scroll face. Temperature differentials on the scroll face may be captured as a thermal image. The location(s) of temperature differentials on the scroll face can be correlated to defects in the module. In preferred embodiments, the subject test methods are non-destructive and can be applied to spiral wound modules in either a dry or wet condition.