[unclebilly]

Your test is flawed.

For water to flow, you need pressure to drive it.

When you shut off the master supply valve, the pressure in your system may bleed off due to a leak but since water is basically incompressible, if it bleeds down a pint, your pressure is bled off and there will be no further leakage (unless there is a leak at a low point). If you have a pressure tank in your system, the pressure tank volume needs to bleed down too.