There are three basic definitions of water pressure that we should be aware of.
General Water Pressure
General water pressure is the force in the water reticulation system of the building created by either gravity or by pumps.
Static Pressure is the force generated by a no flow condition (i.e. just the pressure of the water in the pipes, not when it is flowing).
Flow pressure is the residual pressure or force within the line when the water is flowing.
Did you ever wonder what that banging noise was in your wall? That noise that is impossible to track down? That noise is what you hear when the water flowing in a system is very suddenly stopped. It is like a large bang often with another couple of bangs after it. It often sounds louder because of loose or poorly installed pipework. This is called water hammer.
Solenoid valves, these are valves that may be in dishwashers or clothes washing machines, that are instant in the opening and shutting of the valve, are prime causes of water hammer.
The problem can be fixed by installing a water hammer arrestor valve.