Fluid flow detector with tethered drag block

A method and system for monitoring, measuring and affecting fluid flow within a pipe element of a plumbing system. One version is attached proximate to, and installed through, a hose bib of a building water plumbing system. The device includes water flow sensing and monitoring modules that are coupled to a drag block. The drag block may be configured to be deployed and deformed within a fluid pipe as directed by a controller or by manual control. The controller is optionally communicatively or bi-directionally communicatively coupled to an external receiver or transceiver by wireless means. Data collected by the device is analyzed to detect leaks in the plumbing system. The device may include a power source, such as an electrical battery, a solar energy collector, and/or a wind energy collector.