Why Are Showers So Sensitive?

(Last Updated On: August 9, 2022)

Hopefully, so long as you have water and stuff, you take showers when it gets hot out. You should also be taking showers when it’s cold, but you know. Shower temperature is a pretty common complaint; you know how to nudge the dial just a tad and the water goes from a little too cold to boiling lava hot. Or just a little too warm to just an ice bath. So why are showers so sensitive?

How Showers Work

So there are two potential reasons your shower temperature is changing so much. One, your shower is finicky. Two, we’re actually all just sensitive. Let’s start with the shower. 

At a very simple level, showers have a hot tap and a cold tap. These sit at opposite temperature extremes, and you’re not going to want your shower at the hottest possible or coldest possible temperature. So the hot tap and cold tap get turned on together when you open your shower valve, and they mix together. They will reach thermal equilibrium together after a bit–which is why it often takes a minute for your shower to get to the desired temperature after turning it on. 


There’s a pretty good chance you have a pressure-balanced valve in your shower. Feeding into your water supply is really hot water and really cold water, and turning the dial changes how much hot or cold water is sent to your shower. The valve keeps the pressure coming out of your shower constant, so when you add in some hot water the pressure doesn’t skyrocket. It also keeps the temperature of your water from changing when someone, for example, flushes a toilet. When a toilet is flushed, lots of cold water is used at once. This can dramatically reduce the cold water your shower is receiving, and if no cold water is going to your shower the pressure of cold water going to your shower drops dramatically as well. If your shower wanted to maintain the same water pressure coming out, then the pressure of hot water would briefly increase dramatically to make up for the cold water that isn’t there anymore–which can burn you. A pressure-balanced valve compensates for this by keeping the pressure from the other tap (in this case, the hot one) from shooting up so you don’t have to worry about being burned when someone else uses water. Sometimes they’re required for this reason. 

Mixing Valves

If your shower does have a huge temperature change when someone flushes the toilet, you probably have a mixing valve. These are a lot simpler than pressure-balanced valves, they just take hot and cold water at once, and mix them so they’re the temperature you want. Simple enough. Except mixing valves don’t compensate for anything like pressure-balanced valves. When there’s a pressure imbalance from one tap sending less water to the shower, your mixing valve doesn’t really do anything about it. So in our previous example with the hot water, the hot tap just pours into your shower when the cold tap is diverted. 

Why Does it Change So Easily?

Well, unfortunately the water temperature in your shower isn’t changing easily due to a property unique to your shower. Turns out, we’re all actually just super sensitive. 

The human thermal sensory system reacts to even the most minute changes in temperature. Different parts of your body are more sensitive to temperature than others, with the most temperature-sensitive parts of your body being your cheeks, lips, and fingertips. The least sensitive, by the way, is your feet. Along the more sensitive parts of your body, you can distinguish between a temperature change between 0.02 and 0.07 degrees Celsius

What this means for you is that the temperature you consider warm and comfortable is very specific. Even a tiny change in temperature is enough for you to detect, and if you can detect it you’ll find it either too hot or too cold. The reason why it feels like the temperature is changing very dramatically is because we’re not only very good at detecting small temperature changes, but we also react strongly to sudden temperature changes.

So how does human temperature sensitivity relate to your shower handle? Well it means most of the dial is… pretty useless. Everything up to your temperature of choice is way too cold, and anything past it is too hot. Let’s imagine moving your shower handle changes your water temperature linearly. That’s to say, imagine that moving it one inch to the left makes it exactly 1 degree Celsius warmer and moving it to the right makes it exactly 1 degree Celsius colder. Because your shower’s temperature range is so wide (up to 140 degrees Celsius) and your temperature preference so exact, the handle position for your ideal shower temperature is going to look something like this.

Speaking of showers, ever have random thoughts in the shower? Anyway here are some.

About the Author:

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Kyler is a content writer at Sporcle living in Seattle, and is currently studying at the University of Washington School of Law. He's been writing for Sporcle since 2019; sometimes the blog is an excellent platform to answer random personal questions he has about the world. Most of his free time is spent drinking black coffee like water.