A vapor recovery line that passes a proper pressure test gives the station owner years of quiet service. One tested carelessly gives intermittent balance complaints that no one can trace.
Choosing the Test Medium
Inert gas is the standard choice. Compressed air works where regulations allow, but moisture in the line during cold weather can freeze at restrictions. Whatever medium is used, connect through a regulator and calibrated gauge, not the shop compressor alone.
Test Pressure and Duration
Test pressure typically reflects operating conditions with a margin, and hold time must be long enough for temperature effects to settle. A line that drops slightly in the first half hour then holds steady is showing thermal contraction, not leakage. Note temperature at start and finish to interpret readings correctly.
Isolating Sections
Test in sections when possible. A single drop reading across the whole system cannot tell whether the leak hides at a dispenser, a coupling or a tank fitting. Section isolation turns an afternoon of guessing into a targeted check.
Reading Results Honestly
Gauges lose accuracy near the bottom of their range. Use a gauge whose mid-scale sits at the test pressure. Soap solutions find the leak once a drop confirms one exists; do not rely on bubbles alone for acceptance, since small weeps at buried joints may not show.
Recording the Test
Log the medium, pressure, duration, start and end readings, temperature and isolating valve positions. This one-page record settles disputes during commissioning and anchors future diagnostics when readings drift.