A traditional type of shower valve is the mixing valve, designed to draw water to the shower head from the hot and cold taps. Mixing valves are primarily found in older houses and are less popular in newer builds. 

A mixing valve cannot regulate sudden changes in water pressure, so someone showering runs a risk of getting scalded if a sink, toilet or washer unexpectedly draws cold water. 

Tip: To help avoid scalds in a home with mixing valves, lower the water heater thermostat to 120 degrees Fahrenheit. 

Pressure balancing valves, also called mechanical or anti-scald valves, are the most common types of shower valves. A pressure balancing valve is designed to rebalance the water pressure to keep the shower from becoming excessively hot. The mechanism contains pistons or diaphragms built to move with fluctuations in water pressure to balance the hot and cold water supplies. These can keep the water temperature constant within 2-3 degrees Fahrenheit. 

Most pressure balancing valves have a single control and a handle. Water becomes warmer or colder when the valve is turned left or right. 

Tip: Some older homes may not be equipped with plumbing durable enough for pressure balancing valves. 

Thermostatic valves are designed to maintain both water pressure and temperature. The thermostatic valve mechanism contains a thermosensitive element that adjusts the flow of hot or cold water based on changes in temperature. Many thermostatic valves include a dial that allows users to preset the water temperature. 

Thermostatic valves are also popular shower valves, but can be more expensive than pressure balancing valves. 

A thermostatic shower valve often includes a volume control feature that allows users to set the amount of water coming from each water outlet. 

Diverter valves are designed to direct water to the required shower components from a bathtub, allowing for bathroom to have a tub shower combo. There are three shower diverter valve types. 

• A tee diverter consists of a pull arm on a tap, usually the bathtub faucet. When the water reaches desired temperature, the user pulls the arm to block the tap and the diverter valve directs the flow to the shower. 
• A two-valve diverter uses a rotating control for hot and cold, and a second control to divert water between the tub and the shower. 
• A three-valve diverter allows individual adjustments of cold and hot water, plus a central knob to divert water between the tub and the shower. 

Transfer valves allow water to flow to multiple outlets, such as a handheld shower head, without shutting off the main shower. Some transfer valves allow the use of multiple components at a time.