Since having our water meter fitted our pipes (quite often) make a terribly loud HUUUUUUUUUUUUUU noise when the water is turned on. The water board have told us to run our mains tap for one hour. One hour, really? An arbitrary amount of time set by man just happens to exactly fit how long we need to do this for? Not 53 mintes or 1h24m? And that is going to fix it, is it?
Yeah, sounds like trapped air, especially if it’s moving up the house.
Is your washing machine plumbed into the hot water, or just the cold? If it’s the latter, it implies that the air is probably trapped in the cold water system, which is better than it being in the hot water, at least.
The rental place I hire a dishwasher from sent a “plumber” round to look at it. He clearly wasn’t a plumber but a generalist technician. This isn’t the anecdote.
Anyway, as he was enjoying the Hario dripper coffee I had made him, he asked what I did for a living. His response was “Patents, eh? That must be tedious.” In my own home! Drinking my good coffee!
I mean he’s not wrong but that’s not the point.