ARGH! With a family of 7, we are getting tired of hollering at the 16 yo and the 13 yo to get out of the shower. I have often found coin operated controls for showers while camping….
Bro: I know da feeling o’ havin’ yo’ chil’ns usin’ up all dat hot water wiff dem long showers. Yo idea ’bout dat coin operated valve at da campin’ sight iz cool,..but be careful not ta git caught getting uh hold o’ it.. otay buh-weet? Elzo
Another way is “one warning and then the tap to the hot water system is turned off”. The threat might not move them, but a cold shower in winter make them think a bit