How Does a Faucet Control Water Temperature?

One of the best things about modern plumbing is that it kind of works. You don’t necessarily have to think about where your water goes when it drains, or how a faucet can produce hot and cold water, but when you start thinking about these things, it can be hard to figure out how everything actually works.

Take hot and cold water for example, you know you have a water heater so where does the cold water come from? And how does turning a knob or two get you the right temperature inside when you set the thermostat on the water heater outside? Now that we’ve got you thinking, let’s solve this plumbing mystery…

How Your Home Gets Hot And Cold Water

Whether you have individual knobs for hot and cold water or one master knob that controls everything, your faucet is connected to two water lines: the hot water line that runs from your water heater, and the cold water line that runs from your main water pipe.


Of course, turning on only the cold water nozzle will give you only cold water, and turning on only the hot water nozzle will give you only hot water. By turning both handles you’ll allow the water from both faucets to mix before it comes out of the faucet, according to your chosen ratio of hot to cold water.

But believe it or not, the hot and cold handles don’t actually control the temperature of the water. Depending on your faucet, there are some combination of different valve-like devices, such as mixer taps, single handle mixer taps, temperature control valves and thermostatic mixing valves, all of which are operated by the handle(s) to give you the perfect shower temperature.


So there you have it, the answer to a plumbing question you didn’t even know you had! If you are having trouble heating warm or hot water, it may be time to start shopping for a new water heater. When choosing a hot water heater, you need to consider the size of your home, the number of people living in your home, the amount of hot water you use daily, and even maintenance.

If you need help making the right choice, give us a call or contact us online at and  we’re here to help with all your plumbing and repairing needs.


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