Venturi and a pin hole in a water pipe

[ramonegumpert]

Dear Experts,

I was looking at Venturi effect and a question popped into my mind.

When I use a water hose and turn on the tap, the water rushes out of the hose. If there is a break along the hose, eg. a small puncture, some water would also leak through this hole am i right? At least this is what i think.

But according to venturi effect, air should be sucked in and flow out of the hose.

Or is my assumption wrong?

regards
Ramone

 

[rcgldr]

Since the hose is constant diameter, the pressure in the hose is highest at the tap end, decreasing in pressure as water flows to the exit end due to friction with the walls of the hose, but still higher than ambient pressure outside even at the exit.

http://en.wikipedia.org/wiki/Darcy–Weisbach_equation

However here is a link to a device that has the effect you want. It's a vacuum pump that operates off a water tap. There a smooth tapered cone that reduces pressure and exits into a chamber with second connector on the side. The reduced pressure, (and probably momentum of the main flow combined with viscosity) in the chamber will draw in air and/or water into the side connector, and both flows exit out the connector at the end (which can be closed in order to have water flow out the side connector to fill something). In this case the device is intended to be used for an aquarium, but devices like this date back to the 1930's to be used to fill and drain wash basins (note the us patent prior references). The link to the candian patent eventually leads you to an internal drawing of this device.

http://andysworld.org.uk/aquablog/?postid=247

Firgure 4 in the drawing shows it in drain (venturi) mode with the bottom open. Figure 5 shows it in fill mode with the bottom closed.

drawing.gif