Well, we've lived here for almost 29 years and it hasn't changed.
It would be extremely annoying if there were a mains feed, as, apart from the cold tap in the kitchen, all our water goes through a softener and my understanding from more than one heating engineer is that you don't want softened water in central heating as it eats its way through the heat exchanger much faster than unsoftened water.
Besides, the heating engineer expressed concern that there must be a mains feed and it took some convincing by me that there wasn't. He drained the system and we weren't flooded.