Flood Master, Smart Home and Amazon.com all sell shut-off valves for home water heaters. Many of the products offered come in kits that include a shut-off valve, a leak sensor and an alarm that sounds when a leak is detected,.
Most of the units claim to be "lead free" and to be made from non-corrosive materials. Installation is generally considered easy, and a professional plumber is not needed. Flood Master offers accessories, including cable extensions and wired sensing pucks that allow up to 5 additional sensors for a wider area of coverage. A sensing rope for sub-floors and low tanks, as well as an automatic dialer that sends and receives alerts when a fault is detected are available options.