The Pioneer of Modern Leak Testing

Pressure Decay Leak Test

What is Pressure Decay Leak Testing?

The Pressure Decay test, also known as gauge decay, absolute pressure, leak drop or delta pressure leak test.  This test method measures the drop in pressure on a gauge (transducer) during the leak test.  Pressure decay leak testing is used to test products for leaks by trapping pressure inside a product and then measuring pressure loss.

In this test method the component is pressurized with air and the pressure transducer monitors the pressure for negative changes. Any pressure drop indicates a leak. The pressure change from the first measurement to the last measurement made during the test phase of a test is what is important.

The test is very fast, a matter of seconds, and is therefore popular for leak testing in high-volume industries such as automotive components, castings, medical devices and consumer goods.

How is a Pressure Decay Test performed?

To begin the Pressure Decay leak test, the test part [TP] is attached to the test port. The tester then pressurizes the part with pressure [+P] to the desired test pressure set by the pressure regulator [R1] during the Fill step by opening valves [V1] and [V2].

Upon completion of the Fill step, pressure is trapped inside the part as [V2] closes.  After a slight delay, [V1] closes allowing the line between [V1] and [V2] to vent to atmosphere through [V1] allowing any leakage through [V2] to cause the tester to see this leakage and fail all tests. The extra valve allows for a fail-safe configuration.

Trapped pressure inside the test circuit is held through the Stabilize step and then measured by the testers pressure sensor [PS] during the Test step.
If the part exceeds the programmed leak tolerance (pressure drop over time or quantified leak rate), the tester’s display indicates the reason for the test failure and displays the pressure loss or leak rate in user defined units of measure.

Upon completion of the Test step, pressure trapped in the part is vented to atmosphere through [V1] by opening [V2] during the Vent step, and the tester is ready for the next test.

Pressure Decay Test Pneumatic Diagram
Pressure Decay Test Pneumatic Diagram

Learn more about Pressure Decay Leak Testing from the video below:

Which Uson Leak Testers Can Perform A Pressure Decay Test?

Sprint mD air leak tester

Sprint iQ leak and flow tester

Optima vT leak tester

Qualitek mR air Leak and flow Tester

Vector Leak and Flow Tester

Uson Innovative Systems

Have Questions? Need a Quote?

Ask Our Experts

Which Uson Tester is Right for Your Project?

Compare Models & Specifications

Find Local Support

Find A Uson Rep in Your Area

Contact Us


Uson L.P. - Corporate

8640 N. Eldridge Parkway
Houston, TX 77041 USA

Tel: +1-281-671-2000
Fax: +1-281-671-2001


Uson UK – Europe

Western Way
Bury St. Edmunds
Suffolk, IP33 3SP United Kingdom

Tel: +44-1284-760606
Fax: +44-1284-763049


Uson – China

Room 601, 567 Lan Gao Road
Shanghai, 200333, China

Main: 021-583 65859, 021-583 59187
Fax: 021-583 59185, 021-337 73559