What has been done in the past:
The showers are flow thru electric water heaters with a single on/off valve control. The shower temperature has been regulated by setting the water heater thermostat. After the heaters have gone unused for a half hour or so the temperature is a moderately warm 105 degrees. After several showers in a row, the water temperature heads downward. Also, some attendees like to turn up the thermostat which can cause uncomfortably hot temperatures.
What the problem to be solved is:
Better regulation of the water temperature.
Evaluation of implementation: