I was going to post a similar thread, oh! weeks ago

. I worry about the fact that when I was looking after a neighbour's dog, the tap had been left on 'hot' so I scalded myself. Not badly but there wasn't any warning

. If the cold tap comes from the mains, i.e. fresh water on tap; but many systems also have hot water via a tank in the roof, it's easy to forget that dead birds/mice can find their ways into the tank in the roof

.
What's wrong with boiling a kettle? There must be run off which ever system is in use, because there's always water left in the tap. On the other hand, if it's from a tank below the sink, there isn't all that distance from the tank in the roof for hot water ....... which to me seems such a waste, the need to run water to get warm too.