Why Understanding Pressure Decay Leak Test Is Important?

Pressure Decay Leak Test (PDLT) is a method for determining the suitability of cylinders, pressure relief devices and metallic piping systems for safe operation by detecting leaks. It is also known as a practical leak test or a hydrostatic test. In this test, under prescribed conditions of pressure and temperature, the gas in the system being tested is allowed to escape through all possible leaks and determine what proportion of it escapes at different rates (gas volume per minute). The PDLT can be applied to both closed system and open system.

Test Principle

The pressure decay test is a test to determine the integrity of the seal of a flexible diaphragm. To conduct this test, we place a pressure sensor on the diaphragm and measure the pressure decay over a period of time. A typical duration for this test is about 2 minutes.

Instruments and Test Materials Required

Pressure decay leak test is a very important test to know about. The test principle is to measure the pressure decay and it’s done using a pressure decay leak test kit. A pressure decay leak tester can be used to detect leaks in valves and pipelines in a system. The instrument will give us results based on how much gaseous substance is escaping through the pipeline or valve.

A pressure decay leak meter works by measuring the decrease in ambient air pressure resulting from gaseous loss through an opening such as an escape hole or crack in an underground pipe line system or tubing system.

pressure decay leak test


You can conduct a pressure decay leak test by following the following steps:

  • Ensure that there is no air in the system.
  • Connect the pressure decay leak tester to an external source of clean compressed air and make sure that it is turned on.
  • Slowly open all valves one by one and observe if there is any change in the reading displayed on the gauge while doing so. If there are no changes, then you may continue with your work; otherwise re-check for leaks again.
  • Close all valves and turn off your compressor before disconnecting any hoses or gauges from it.

Test Results Analysis

  • If your results are not as expected, you should revisit the procedure and make sure that you performed it properly.
  • If your results are as expected, congratulations! However, understand that this does not mean that there aren’t any leaks in your system. You will want to perform this test again at least twice more before making a final decision about whether or not there are any leaks in your system.


In conclusion, we can say that understanding pressure decay leak test is important because it helps us to understand the quality of the system. In addition, it helps us to find out whether there are any potential leaks in the system or not. There are various instruments and materials required for performing this test which are easily available in market and online stores at affordable prices.