But in this case, Originalsaltedpeanuts, it wasn't the best course of action. In fact, in lots of cases it wouldn't be.
I used the link a helpful pp posted to find the water board. It told me the supplier was a major water board. I visited the appropriate website, which told me that there were no works or incidents in the area. It advised me to call a plumber. So in that instance, I would have then had to call the owner anyway.
As it was, the original website was incorrect, and the major water board wasn't the supplier. The supplier is a much smaller operation supplying around 250 houses in the village. I wouldn't have known that without calling the owner, who was then able to quickly call her neighbour, who she knew would be up early (I don't have that inside knowledge, having been here less than a week!) and find out what the issue was.
And even if the above wasn't the case, and there had been some sort of incident which would mean we would be without water for an indeterminate amount of time, I still would have had to call the owner to at the very least let them know. Ultimately it is their house, their responsibility and it would have been up to them how to handle any given scenario.
So calling the owner is the best thing to do. And being unpleasant for no reason other than to try to make someone else feel small or stupid never, ever is.