The dye test is only effective if you have some idea of where the leak is. If you are unsure of the general area of the leak, the dye test is unreliable. The dye test is cost-efficient. Still, it is simply a precursor to more reliable and in-depth testing methods like the pressure test.
A pressure test is something that only skilled people should do since there is inherent danger in pressurizing plumbing lines. Pressure test pipes is to narrow down the leak location further.
When a leak is confirmed by the results of a Pressure Test, we can pin point exact location of the leak by performing Sonic Leak Detection.