Think of the bathtub at your house. It is simple, right? You turn the taps and the water comes in. You unplug the drain to take the water out.1

Seems straightforward, yes. But let’s draw a map to see where your bathtub works in the system. When you open the drain, where does the water go? If you live in an urban environment, the water enters an elaborate network of pipes in the municipal infrastructure. The water is treated. It is then discharged back into the ecological system, reentering the hydrological cycle of the planet once again.

Water, in turn, is harvested, chlorinated, pumped back through the municipal supply lines, and fills up your bathtub again. It is entirely possible that some molecules of water disappearing down the drain might come back into your bathtub through the faucets. In other words: your bathtub is not an island. Your so-called ‘simple’ bathtub is not so simple after all. It is directly connected to an immense network of water harvesting, supply, treatment, and discharge. And this process, in turn, is connected to the planet’s hydrological cycle.2

You have a desired temperature range in mind for your bath, which means that you have variable inflows — hot and cold. Hot water presumably has to travel from a heater or boiler somewhere, which requires another system of energy inflows and outflows to heat the water. The energy itself, in turn, was generated by a system of inflows and outflows

What makes your bathtub especially complex is that it is part of a network of bathtubs. Sure, on its own it may not seem very interesting, but attach the drain of your bathtub to a maze of pipes that empties into a reservoir along with a few million other bathtubs and you begin to appreciate the seismic influence that bathtubs have on your municipal infrastructure. The next time you are soaking in a hot bath, you might ask yourself, Where did the energy come to heat this water? A lump of coal? A barrel of oil? A split nucleus?

The inflows and outflows of your bathing are systemically interconnected with the inflows and outflows of a vast system of systems. There is nothing ‘simple’ about taking a bath. (For rural readers: even if your water comes from a well or spring, is heated by firewood in a kettle, and tossed behind a hedge or into a septic system, the interplay of systems is no less complex: consider the natural filtration of the well, the photosynthesis of the tree, and the water tables under your yard.)

However, we are still only scratching the surface of grasping the systemic nature of your bathtub. For example, consider the pipe that connects to the drain: where did the raw materials come from to make that pipe? How was the manufacturing of that pipe related to the economy? What laws or legislation that regulate the mining industry or local building codes influenced the creation of that pipe?

Not in exaggeration, you could explain in how everything in the world is eventually ‘connected’ to your bathtub. Your bathtub is part of the system of everything.


  1. Meadows H., Donella. (1997). Leverage points: places to intervene in a system. 

  2. The Water Cycle diagram is in the public domain, provided by U.S. Geological Survey, available at 

Cite this page:
Shelley, James. (2020). 'Bathtub' (in System Thinker Notebook). Originally published on August 5, 2020. Accessed on September 29, 2020. Licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Permalink:
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