Which of the following is not used as an anti-scald device?

A water heater thermostat serves to regulate the temperature of the water in the heater itself, ensuring that it does not exceed a set maximum. While maintaining the water temperature is important to prevent scalding, it does not actively function as an anti-scald device in the plumbing system where the water is delivered to fixtures.

In contrast, a pressure balance valve and a thermostatic mixing valve are specifically designed to combat scalding by adjusting the temperature of water at the faucet based on changes in pressure or temperature. Similarly, flow restrictors help to manage water flow and ensure a consistent temperature by balancing water delivery. Therefore, the role of the water heater thermostat is limited to controlling the maximum temperature at the source, rather than directly preventing the risk of scalding in the plumbing fixtures.