A manifesto on shower temperature control

January 30, 2023

I had a very shower-y shower thought: why does turning my shower handle a tiny bit make such a huge difference in the comfort of the shower? Why are we wasting so much potential control area on water temperatures that no one wants? Who cares about ice cold, mildly cold, cold, or lukewarm water - that entire section of the control is wasted. I propose a more refined and humane control strategy. Kohler, Moen, et. al.: @ me.

The current (broken) state of affairs

Imagine your typical shower control: it likely has a 180° range of motion to control the temperature, which ranges from ice cold to blistering hot. In my home (shower control n = 3), comfortable shower temperature is found in a narrow range of approximately 10°, or 5.6% of the available control surface. Since temperature has a nearly linear relationship with control rotation, most of the control surface creates shower temperatures that are uncomfortable and therefore unusable to humans.

Graph showing theoretical linear relationship between water temperature and rotational angle of the shower control
fig 1. illustration of hot and cold inputs.
This control strategy is so bad, even the graph makes a big Ⓧ.
Graph illustrating a narrow range of shower control positions that results in a comfortable water temperature
fig 2. water temperature vs. rotational angle of shower control.
*comfort zone exaggerated for clarity

In the service of this manifesto (and by extension, in service to all of humankind) I decided to Do A Science and measure the water temperature T as a function of rotational control angle r. The experimental process was as follows:

  1. Rotate the control handle
  2. Record the water temperature
  3. Repeat
Emotionless photograph of camera on tripod pointed at shower handle
fig 3. emotionless digital color photograph of experimental process

Experimental Results

Graph showing approximately linear relationship between water temperature and rotational angle of shower control
fig 4. water temperature (°F) vs. rotational angle of shower control
n = 1

The minimum temperature was 44.4°F (6.9°C) and the maximum temperature was 134.1°F (56.7°C).

A survey of household members (n = 4) found the following:

Survey Respondent Preferred shower temperature
Male, 35-40 years 109°F (43°C)
Female, 35-40 years 113°F (45°C)
Female, 13-18 years 95-102°F (35-39°C)
Male, 9-12 years 109°F (43°C)
Minimum 95°F (35°C)
Average 106°F (41°C)
Median 109°F (43°C)
Maximum 113°F (45°C)


From this data we can conclude that all survey respondants' preferred shower temperature falls in a range of 18°F (7 °C) and this range is controlled by 23° of shower control rotation. This is only 13% of all available control surface. The majority of the control range - 119° (66.1%) - results in a temperature below or well below comfortable shower temperature, which is largely wasted. And one fourth of the control range results in fully cold output.

A better way

Now, imagine that almost any position on your shower control resulted in a comfortable temperature. Imagine dialing in the perfect shower temperature with incredible precision and comfort. You could play your shower like a fine instrument, if only the control allowed you to use the majority of the available range to produce comfortable temperatures.

Graph illustrating a wide range of shower control positions that results in a comfortable water temperature
fig 5. the way it could be

In a perfect world, adjusting the shower control by a small amount would result in a small change in temperature within the comfortable range, and result in a large change in the range that is uncomfortably cold. Compared to figure 4, the graph would be relatively flat and then steep in the cold region.

Graph showing theoretical improved relationship between water temperature and rotational angle of shower control
fig 6. theoretical water temperature (°F) vs. rotational angle of shower control
includes experimental results for comparison

I'm speculating, but it seems very reasonable to design a shower valve that is biased for human temperature preference, and biased against cold temperatures. So reasonable that it seems unlikely that an inspired shower valve designer hasn't tried this already. So where are they? Not in every home, that's for sure.

So here's to the (shower) dreamers, let's imagine a more humanely controlled world together.

The author acknowledges the recent trend of "cold showers" and considers them (a) a trend, (b) undignified, (c) a waste of some life-sustaining solidary time.

This blog is an experiment: less about education and more about documenting the oddities I've experienced while building web apps.

My hope is that you're here because of a random search and you're experiencing something I've had to deal with.

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