It's an honour system. Actually the showers have two mechanisms. One is flow restriction/misting. Though some showers are much better than others. The other is

It's an honour system. Actually the showers have two mechanisms. One is flow restriction/misting. Though some showers are much better than others. The other is a small valve on the shower head which you can use to pause the flow while you soap up. It's convenient because you don't need to reset the temperature each time. It's a normal screw valve to open the flow, it's not a timed system like you'd find in a gym/pool shower. Also there are times over winter when we're allowed extra time, such as when the tanks are being cleaned (and have to be drained). Occasionally "vouchers" are given out as prizes, eg for the annual marathon. I think heckling is more likely because at peak capacity there are 150 people on station and only ~10 shower cubicles per gender. There are 2-4 cubicles per dorm wing, each with up to ~30 people. So there can be some contention and people want to shower after work/before dinner.