Thermostatic Shower Valve: How It Works
One of the worst things that can happen when you are taking a shower is when someone flushes a toilet or kicks on the dishwasher and the shower water turn scalding or ice cold. It can lead to second and third degree burns and with children and the elderly it could mean a trip to the hospital. So, you have two options; 1. Redo your entire plumbing and put in pex lines that are not connected like traditional plumbing but allows you to have dedicated lines to each item that needs water. Or 2. You can install a thermostatic shower valve. This valve is hands down the most reliable way to obtain constant water temperature.
These valves provide accurate control over hot and cold water mixing. One of the best features is the anti-scald device, this will turn off the water if the hot or cold water fail for any reason. The way it works is the thermostat will expand and contract when the temperature and pressure changes with the hot and cold water supplies through the hot and cold water inlet ports.
When the element expands and contracts it will move the slide valve to release the correct amounts of hot and cold water into the valve. Should the cold-water supply fail over a period of time, to maintain a safe temperature, the valve will still supply hot water to the valve. If the cold water failed completely the element would expand completely moving the slide valve closed on the hot valve seat. This will shut down the hot water supply preventing any scalding water from reaching the mixed water outlet or water spout.
Putting in a thermostatic shower valve is absolutely the most cost effective solution and once you realize how it works you will wonder where it has been all your life!