The 131 Series Thermostatic Mixing Valves mix hot and cold water in under-sink installations to protect against accidental scalding for electronic and manual faucets. The series incorporates durable brass construction, a thermostatic wax element, an integral filter for consistent performance, dual check valves to help prevent against cross-flow, and convenient access to the cartridge for easy maintenance. The series include three- and four-port models and two low-lead units.