Water Pressure slow or low?
Water Pressure Defects
In order to get the most meaningful results in relation to inspecting the water pressure, it is good practice to inspect the plumbing fixtures at the highest point in the house. And then move downwards to the lowest level of the building while running water at each fixture for a minute or two. Do not let water run at any fixture without close observation. Do not let water run unattended at any fixture.
Many inspectors will run all of the fixtures in one bathroom at the same time and observe their performance. It is helpful to demonstrate to clients how the shower performs when multiple fixtures are running simultaneously. Clients will be able to determine for themselves whether the performance is acceptable or not. When it is not acceptable, inspectors typically call for correction and further investigation by a professional. www.nachi.org