Fire Suppression, Sprinkler & Safety System Products worked example

Pressure Decay Margin with allowed pressure decay of 13 psi, bar, or kPa: a worked example

Push allowed pressure decay up to 13 psi, bar, or kPa and the picture changes. This example computes every intermediate figure at that operating point. Use it when reviewing leak or hold tests for valves, cylinders, pipe assemblies, tanks, hoses, or suppression modules.

The inputs for this scenario

  • Allowed pressure decay: 13 psi, bar, or kPa (raised for this scenario; the documented default is 5)
  • Measured pressure decay: 2.8 psi, bar, or kPa (unchanged)
  • Reference decay limit: 5 psi, bar, or kPa (unchanged)

Working through the calculation

  • Applying the documented formula (Pressure Decay Margin = allowed pressure decay - measured pressure decay) to the inputs above produces each figure below.
  • At this operating point the engine returns 204 % for pressure decay margin, the number this scenario is built around.
  • At this operating point the engine returns 10.2 psi, bar, or kPa for pressure decay margin amount.
  • At this operating point the engine returns 13 psi, bar, or kPa for allowed pressure decay.
  • At this operating point the engine returns 2.8 psi, bar, or kPa for measured pressure decay.

How this compares with the baseline

  • Against the tool's baseline example, where allowed pressure decay sits at 5 psi, bar, or kPa and the headline result is 44 %, this scenario comes in 364% above the baseline at 204 %.
  • It computes the difference between the allowed decay and the measured decay, then expresses that difference as a percent of a reference decay limit to give a normalized margin. The value of this scenario is the size of the gap it exposes: that gap, priced out over a year, is the budget you can justify spending to close it.

Results at a glance

  • Pressure Decay Margin: 204 % (headline result)
  • Pressure Decay Margin amount: 10.2 psi, bar, or kPa
  • Allowed pressure decay: 13 psi, bar, or kPa
  • Measured pressure decay: 2.8 psi, bar, or kPa

Run it with your numbers

  • Every input above is editable in the live Pressure Decay Margin calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.