Would it not save more water if they asked them to only shower every other day and just have a quick wash the other times?
When I was a lad back in the 1950s we only had a bath once a week. Even that was shared, 3 brothers and we took turns for 1st in . If you were 1st one week you were last the next week and 2nd the week after that. The only source of hot water was the back boiler over the coal fire ,(apart from a kettle.) The fire would be lit on a Sunday to heat water for 'Bath night'.
Your childhood sounds a bit like mine, Eddie. Our mam would do the washing in the dolly tub, then three of us would get in the dolly tub for a 'bath'. Happy days. :o)