Simply replace your existing tub spout and shower head with this HotStop Tub Spout and Shower Head. If water reaches an unsafe temperature, HotStop quickly reduces the water flow to a trickle to avoid scalding. Once the water in the line cools, the flow restarts automatically. This tub spout will replace any tub spout with a diverter. Includes adapters to fit most spouts. Includes HotStop Antiscald Shower Head, which must be installed for the safety feature to work.