What pressure does a garden hose nozzle develop when it is at it's highest rate of pressure from town water?

Question

In other words, if I open the throttle on my spray nozzle from a town water supply of 40psi and I have the nozzle pinched off, what pressure is developed from that nozzle as it is restricted flow through a smaller point?

Answer 1

In general, the pressure would be the same: 40 psi. Hydraulics is a bit puzzling until you get familiar with it. But the pressure will be the same in the entire system, especially if not a lot of water is allowed to flow. But there is a caveat that if you stop the flow of water suddenly, then there is a momentum from the water in the system that creates a brief pulse of higher pressure in the hose. A plastic or rubber hose will expand slightly under this pressure pulse, but then it will force some water back into the main system, and the pressure will equalize to the 'mains' pressure.

Interestingly, water pressure in London is seldom high at all. There are so many leaks in the too-old, and poorly maintained system, that the water company keeps the water pressure at just over 1 bar, just over 14 pounds per square inch, to minimize losses though leaks.