When a pressure system is being tested, it is first sealed and then filled with an incompressible liquid. Depending on the volume of your pressure system and the pressure that needs to be tested, this may take some time.
After that’s done, the technicians then subject the system to a certain amount of pressure for a certain amount of time. This pressurization causes the system to expand and the readings of this change are recorded. The technicians then physically inspect your pressure system to make sure that it is not leaking and that its shape hasn’t been permanently distorted.
Once the results are measured, the liquid from the pressure system is drained. Depending on the results of the test, the technicians will advise you on the next steps that you will need to take to rectify the state of your pressure system.
Most of the time, this involves fixing the problems that the technicians found and then conducting another hydrostatic test to ensure that your plumbing system has been fully repaired.