A piped water supply and distribution system is intermittent when water continuity is for less than 24 hours a day or not on all days of the week. During this continuity defining factors are water pressure and equity. At least 45 countries have intermittent water supply (IWS) systems. It is contrasted with a continuous or "24/7" water supply, the service standard. No system is intentionally designed to be intermittent, but they may become that way because of system overexpansion, leakage and other factors. As of 2022, there was no feasible method for modelling IWS, including no computer-aided tools. Contamination issues can be associated with an intermittent water distribution system. Global public health impact includes millions of cases of infections and diarrhea, and 1560 deaths annually. 
A continuous supply is not practical in all situations. In the short term, an IWS may have some benefits. These may include addressing demand with a limited supply in a more economical manner. An intermittent supply may be temporary (e.g., when water reserves are low) or permanent (e.g., where the piped system cannot sustain a continuous supply). Associated factors resulting from an intermittent supply include water extraction by users at the same time, resulting in low pressure and a possible higher peak demand.