As you may be aware a couple of years back, Australia has severe drought and serious water storage concerns. Various state governments virtually mandated max 4 minute showers, gave free water proof timers and it is now very socially unacceptable to have a long shower. Things like watering your garden, hosing your concrete and washing your car were actually banned and strictly enforced.
I have in my house manual that Australia’s water resources are limited and precious and to respect this with shower times. At least half my guests come from countries you can’t even drink water from the tap but many just don’t care and have ridiculously long showers, don’t put the exhaust fan on and leave water EVERYWHERE. What can you do? I tell them, do the internal eye roll, wait for my money and move on.
I would suggest getting a shower timer, recommend guests ‘respect the environment’ have limit showers to 5 mins and install a water saver head and ignore any bad review. My showers are usually less than 3 minutes, even if I shave or wash hair, but weekends I have baths. These use less water and are better for the environment.
http://www.couriermail.com.au/news/queensland/land-of-the-four-minute-shower/story-e6freoof-1111113123662?sv=a1ed751869715080703fd6819c93972f