We have a combi boiler, which takes a little while (15 seconds or so) for the water to heat up when you turn on the hot tap. I'm usually too impatient to wait, so I wash my hands in the cold water. But in the meantime, the gas still fires on and runs for about 30 seconds, even after I've turned the tap off. The energy crisis has made me realise this is a waste. I need to either be more patient for the hot water, or cut my losses (literally) and use the cold tap instead. What do you do?