⏱ Required Hold Time
📊 Pressure Drop
Result Breakdown
Full Calculation Table
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How to Use the Gas Leak Test Calculator
Choose natural gas or propane. This labels the report; the pressure test itself uses air or an inert gas.
Enter the test pressure and hold time your CSA B149.1 table requires for this system's working pressure, pipe size, and length.
Record the pressure at the start and end of your test hold, along with the actual duration you held the test.
Click Calculate Test Result to compare your readings with those requirements and see the pressure drop and a pass or fail result.
Understanding Gas Piping Leak Testing
Before a gas piping system is put into service, code requires a pressure test to confirm every joint is sound. This isn't a formality. A leak in gas piping, even a small one, creates an ongoing safety hazard that only gets discovered after the system is buried in a wall or already energized, which is exactly the situation a proper pre-service test is designed to prevent.
How the Test Works
The piping system, before any appliances are connected or with them isolated as the code requires, is pressurized with air or an inert gas to the test pressure for that system. The pressure source is then isolated and the gauge is watched for the required hold time. A properly sealed system holds pressure with no drop on the gauge. Any drop points to a leak in the joints, fittings, or piping, or to a temperature change in the pipe, so let the pipe temperature settle before judging a small movement. The test is part of CSA B149.1, the natural gas and propane installation code, which covers piping and tubing systems from the utility connection or propane tank onward. The code also sets requirements for the test gauge, so use one that meets them.
Test Pressure and Hold Time Come From the Code Table
CSA B149.1 does not use one fixed hold time. The test pressure and duration come from a table keyed to the system's working pressure, pipe size, and length, as SkilledTradesBC's gas fitting training material explains; a short run on a 2 psi system might call for 15 minutes while a longer one calls for 60. Because the right figures depend on the code edition and jurisdiction, this calculator asks you to enter the test pressure and hold time from your table, then checks your readings against them.
Test Media: Air or Inert Gas, Never Oxygen
The piping pressure test uses air or an inert gas such as nitrogen or carbon dioxide, and never oxygen, which can ignite oil and grease. The test checks the mechanical integrity of the piping rather than combustion behaviour. After the system passes and is purged and put into service, joints are checked again at operating pressure with leak detection solution or an electronic detector.
What a Failed Test Means
Any pressure drop during the required hold time means the test fails, and the leak needs to be located and repaired before retesting. Leak detection solution applied to joints while the system remains pressurized is the standard way to pinpoint the exact location. After repair, the test restarts from the beginning rather than continuing a partial hold, since the goal is confirming the entire system holds pressure for the full required duration. A leak is a fuel gas hazard, and once appliances are running, the carbon monoxide calculator in indoor air quality covers the separate question of combustion byproducts.
Documenting the Test
A completed gas leak test should be documented with the required test pressure, the starting and ending pressure readings, the hold time, and the test medium, ready to attach to a commissioning report or permit inspection file. This same documentation habit applies broadly across HVAC testing, whether it's this gas test, a refrigerant circuit pressure decay test, or a combustion safety check once the appliance is running, where the flue gas analyzer calculator offers a second view of the flue readings.
Frequently Asked Questions
It depends on the system. CSA B149.1 sets the test duration in a table keyed to working pressure, pipe size, and length, so a short run might need 15 minutes and a long one 60. Enter the hold time your code table requires and this calculator checks your actual hold against it. Always confirm the figure against the code edition and jurisdiction in force.
Test pressure also comes from the code table for the system's working pressure, and it is set well above normal operating pressure so that small leaks show. The pressure test uses air or an inert gas such as nitrogen or carbon dioxide, never oxygen. Confirm the figure for your project in the code edition and jurisdiction in force.
A pass requires reaching the required test pressure, holding it for the full required time, and showing no pressure drop on the gauge. This calculator treats any recorded drop as a failure, and a small drop is worth rechecking after the pipe temperature settles, since temperature changes move the reading.
Not for the pressure test, which uses air or an inert gas such as nitrogen or carbon dioxide, and never oxygen. After the system passes and is put into service, leak checks at operating pressure with leak detection solution or an electronic detector are a normal part of startup. Follow the procedure in the code edition in force.
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