How can I determine what my water pressure should be set at?

100 psi is about 7 bar (i.e. equivalent to a column of water 70 metres or approx 210 ft high). This is a very high pressure for supply coming into a house. Pressures above 3 bar (30 m) can damage fittings or at least cause greater wear on taps etc.
If you have a PRV, the downstream pressure should be set no higher than 2.5 to 3 bar.
Of course the pressure drops when you open a tap. Energy stored as pressure behind the closed tap is converted into kinetic energy of the moving water as the flow starts.

J
March 2008