While maintaining a minimum level of service and rapidly restoring services to normal are key components of critical infrastructure (CI) resilience, who should and how to define these parameters remains under debate. Rarely solicited in the debate, yet integral actors in CI resilience, is the general public. In response to this, this paper presents a questionnaire-based methodology for determining public tolerance levels for service reduction and recovery rapidity. This paper explores this under-researched area using a case-study of the Barreiro Municipal Water Network. It draws on key themes that emerged from the literature as well as interviews with the CI operators in order to develop a tolerance questionnaire, implements said questionnaire (N = 1005), and analysizes the results. Results demonstrate that the methodology works for collecting tolerance levels, that when taking into account vulnerable groups, public tolerance levels appear higher than CI operator capability and that communication expectations are high.