Quote:
Originally Posted by stomachmonkey
I’ve never seen a plumbing system that consisted solely of a straight pipe with the open end pointed up.
By your logic we’d never have to bleed our brake systems because all the air would escape on its own.
Why doesn’t it?
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You’re not understanding this at all.
You have a pipe supplying water to something in your house. At one end is the valve, faucet, whatever it’s in your sink, toilet, shower, wherever the pipe ends up.
What’s at the other end?
If you think about it for half a minute at the other end is a pump or water tower, miles and miles away. There are no closed valves between your pipe and whatever pushes the water at the other end. I’m oversimplifying things but i’m doing so, so that you understand.
If the water at your end of the pipe contracts because it cools, that volume is immediately filled by more water being pushed into the pipe from the city supply end.
In your granny’s jar you will note that she left a little head space above the liquid level for air. After the contents of the jar were heated, she screwed the lid shut and has the air and contents of the jar cooled, it creates a partial vacuum in the air pocket. The jar was a closed system, there was nothing more coming into the jar.
And, just for the plumbers, we’re ignoring that modern house is may have water hammer arrestors that older houses don’t, etc.