Temperature Regulating Valves
There are tens of millions of code compliant shower valves, sometimes referred to as anti-scald shower valves, installed right now that can potentially scald people.
The term "anti-scald" valve is often used to describe a code compliant shower valve, but it is not anti-scald if it is not adjusted properly.
A scald can occur with one of these code compliant valves right out of the box. That’s right! It is possible to buy a code compliant temperature and/or pressure compensating type shower valve that is intended to prevent you from getting scalded and you can get scalded with it right out of the box if you just install it without adjusting the temperature limit stop after the installation is complete.
Scalding is more likely to occur in an older building with a non-code compliant shower valves.
Non-code compliant shower valves are generally two handled shower valves that do not have a pressure compensating (pressure balancing) or temperature actuated (temperature compensating) element to compensate for changes in incoming pressures or temperatures. Non-code compliant shower valves can also be a single handled mixing valves if it does not have temperature or pressure compensating components or maximum temperature limiting devices built into the valve.
Most manufacturers have instructions in their literature with illustrations on how to properly adjust the limit stop on their shower valve. The limit stop is slightly different on each manufacturers shower valve. Some have a set screw that limits the distance the valve can open. Other models have a rotational limit stop with a set screw and a key. Still others have a tooth and spline gear arrangement with a limit stop protruding.
To set the limit stop on a shower or tub/shower valve, follow these steps:
1. Let the water run until both hot and cold water is fully mixed.
2. Rotate the handle fully to the hottest position.
3. Place a thermometer in a plastic container, and hold the container in the water stream.
4. If the water temperature is above the maximum temperature allowed by the local plumbing code remove the handle and adjust the limit stop to reduce the maximum water temperature a safe temperature or a temperature at or below to below the maximum allowable temperature.