The tragedy of the commons: nobody cleans the society water tank

The society group has been busy all week. Someone posts a photo of brownish water from the kitchen tap. Ten people reply "Yes, same here" and "Tank needs cleaning." Two send a thumbs-up. Then the chat goes quiet, and the tank stays as it is.

Forty flats drink from that one tank on the roof. Every flat agrees it should be cleaned. Each one waits for the secretary, and the secretary waits for the committee.

What the model is

A shared thing belongs to everyone, so looking after it belongs to no one in particular. Each person's small share of the effort feels too small to start, and each person's small share of the neglect feels too small to matter. The thing slowly gets worse, though nobody wanted that.

This is called the tragedy of the commons. The ecologist Garrett Hardin made the phrase famous, using a village pasture that every herder lets their cattle graze on. The political economist Elinor Ostrom later studied shared fields, forests and water in many places. She found that communities can look after a shared thing well, when they set their own clear rules.

The tank, step by step

Meera lives on the fourth floor in a Pune society. She is not lazy and neither are her neighbours. Her husband's office is busy, the Hegdes' daughter has exams, and the old couple on the ground floor assume the committee has it in hand.

Here is what the model shows her. Nobody is a villain. The problem is that the job has no name on it. "The tank should be cleaned" is a wish. "Flat 402 books the cleaner on the first Sunday" is a task.

So Meera does one small thing. She does not demand that someone take charge. She posts a plain list in the group: the cleaning is due every three months, here are four volunteer flats in rotation, and each one books the cleaner, collects an equal share from every flat and posts the receipt. Anyone can swap a turn. The old couple are asked to hold the receipts, because they are home all day and like being useful.

That is close to what Ostrom's work points at. The users know the thing best, the rules are simple and visible, and everyone can see whose turn it is.

Where it goes wrong

A rotation can fade after two rounds. If nobody checks the list, it becomes one more forgotten message. It also does not fix things that really need an expert or a decision from the whole society, such as a cracked tank or a disagreement about money.

The model can also make you suspicious of every neighbour. That is not the point. A missing name is often enough to explain a gap, and a bad neighbour is not needed.

One thing to try today

Pick one shared thing in your life: the office fridge, the family WhatsApp group's monthly gift, the flat's cleaning help, the common bathroom. Before tonight, write one line that says whose turn it is this month and whose turn it is next month. Send it to the others and ask if the order suits them.

This is a way to think, not financial, medical or legal advice.

Each Sunday: one mental model and one real decision to try it on. Find more in the /models library.