How Do Faucets Regulate Water Temperature?

Today’s Wonder of the Day was inspired by Natalie. Natalie Wonders, “ How can your shower change the temperature with only the turn of a knob? ” Thanks for WONDERing with us, Natalie!

When it's almost time for dinner, you head to the kitchen sink to wash your hands. The water gets nice and warm as you suds up and get clean. Shortly after, you return to the sink with your cup to fill with cold water. Have you ever WONDERed how those faucet handles are able to change the temperature of the water coming out of the spigot?

If you look around your house, you'll probably find several faucets. In addition to the kitchen faucet, you'll also find faucets in the bathrooms. In fact, most bathrooms will have a faucet in the sink and one in the shower or bathtub.

Not all faucets are the same, though. Some may have two handles: one for cold water and one for hot water. Other faucets may consist of one handle that you keep turning in one direction to make the water hotter.

When you turn on a faucet, water comes out immediately. This is because there is always water running through the plumbing system in your house. It's kept under high pressure. Experts recommend that most modern home plumbing systems should maintain an average water pressure of 40-80 pounds per square inch. However, some local water utilities supply water at much greater pressures, such as 100 pounds per square inch or more.

When a faucet is off, the handles have been turned to the point where a stopper has shut off the flow of water. Once you turn the faucet on, the stopper is opened to allow the pressurized water to flow out of the spigot.

Depending upon which handles you turn and how far you turn them, the water can come out anywhere from very cold to extremely hot. The faucet handles themselves, though, don't control the temperature of the water.

Faucets are supplied with water from two different water lines, one cold and one hot. The hot water line usually comes from a heat source called a hot water heater. The maximum temperature of the water is controlled by a setting on the hot water heater.

Depending upon exactly what kind of faucet you have, different valve-like devices, such as mixer taps, single handle mixers, temperature control valves, and thermostatic mixing valves, are used to regulate the temperature of the water before it comes out of the spigot.

Turning only the cold water handle will give you only cold water directly from the cold water line. Likewise, turning only the hot water handle will give you hot water directly from the hot water line. Turning both handles (or turning a one-handle faucet partially) will allow water from both water lines to mix before coming out of the spigot, resulting in water at a certain temperature dependent upon the ratio of hot to cold water.

There are hundreds of different types of faucets manufactured for use in homes and businesses. Hot taps are usually associated with the color red and may feature a red H on them. Cold taps, on the other hand, are usually associated with the color blue and may feature a blue C on them. To simplify things further, the hot tap is usually on the left and the cold tap on the right, per building code regulations.