How To Pressure Test a Gas Line

What is Gas Line Pressure Testing?

Gas line pressure testing is an essential safety procedure to verify the integrity of gas piping systems.

The process involves pressurising a natural gas line well above the normal pressure levels, typically using an air-nitrogen mixture or pure nitrogen.

Plumbing codes stipulate that gas pressure tests are compulsory prior to operating newly installed gas infrastructure.

The test applies pressure typically threefold higher than the operating level and sets strict limits for acceptable pressure decreases over a defined time. While minor pressure fluctuations may result from pipe expansion or temperature variations, these should not suggest leaks unless they exceed acceptable thresholds.

Licenced plumbers and gas fitters perform comprehensive pressure tests on gas systems, including the gas meter, using specialised equipment for monitoring, to ensure safety and compliance.

When to Perform Gas Line Pressure Tests

Gas line pressure testing is necessary in several crucial circumstances:

• When any new gas piping systems are installed - Pressure tests verify integrity and safety before operation.
• After repairs, alterations or additions - Tests ensure any disturbances did not compromise the system.
• During routine maintenance of gas appliances, such as water heaters, to reconfirm the system’s integrity.
• For appliance fuel conversions, like switching from electric to natural gas hot water systems, it’s crucial to account for the unique pressure specifications of each gas.
• Following nearby construction shaking - Vibrations risk loosened joints.
• After severe weather events or natural disasters - Storms and earthquakes may damage buried pipes.
• When installing a new gas line or buying or selling a home - Tests reassure owners of system soundness and the absence of any gas leak.
• When installing new appliances - if gas odours emerge, it signals potential leaks necessitating a thorough investigation.
• When appliances display issues - Improper appliance operation can reflect piping problems.
• As dictated by applicable legislation - Codes often mandate testing timeframes.

The necessity for air pressure testing in the context of gas systems is underlined by these practices, affirming its key role in preserving the integrity of piping systems and preventing hazardous gas leaks.

Safety Considerations

Rigorous safety measures govern gas line pressure tests, complying with industry standards such as AS/NZS 5601.1 to mitigate risks. Only a skilled gas fitter with calibrated equipment should undertake these critical tests.

• Isolating the test section from the active gas line.
• Sealing open ends to prevent the backflow of high test pressures.
• Ensuring adequate ventilation to disperse any accumulated gases.
• Employing gas detectors to vigilantly monitor for hazardous gas leaks.
• Adhering precisely to prescribed test pressures and durations.
• Watching pressure gauges to verify integrity.
• Using protective gear such as goggles and gloves for safety.

Surpassing the designated test pressures risks pipeline ruptures and hazardous pressure spikes. A significant drop in pressure may allow subtle flaws to go undetected. Strict conformance certifies safety before reconnecting gas supplies.

How to Perform a Gas Line Pressure Test

To perform a gas line pressure test, follow these key steps:

Preparation

1. Acquire the necessary equipment including a compressed air/nitrogen cylinder, hoses, pressure gauge, pipe caps, and leak detection fluid.
2. Isolate the segment of gas line under test using secure methods like screw caps or flanges.
3. Install injection and monitoring fittings like valves, a pressure relief device, and connect the pressure gauge to monitor for low pressure.
4. Confirm all outlets are sealed to retain the pressurised gas.

Conducting the Pressure Test

1. Confirm all nearby appliances are switched off to minimise gas usage during testing.
2. Open the valve on the pressurised air/nitrogen cylinder to start raising the system pressure and attentively manage any drop pressure scenarios.
3. Continue elevating pressure steadily until it is greater than the normal operating pressure, to prevent any significant pressure drop in the gas system.
4. Shut the cylinder valve to cease additional pressurisation.
5. Maintain the test pressure, allowing for no more than 3 psig reduction for a duration of 10 to 15 minutes.

Analysing Results

1. Monitor the pressure gauge closely throughout the test.
2. Test pressure shall remain steady with no drops greater than 3 psig, to meet psi test protocols.
3. Sudden pressure decreases are likely indicative of leaks that must be identified and repaired.
4. Mark and repair faults before starting the process over from the beginning.

Test Preparation

Performing effective gas line pressure tests requires careful preparations beforehand, including:

• Isolating the section of pipe undergoing testing using screw caps or flanges.
• Installing injection points, monitoring fittings and a pressure relief device.
• Sealing all outlets and open ends so pressurised gas cannot escape.
• Ensure the accuracy of testing equipment by verifying it adheres to industry standards and holds current calibration certifications.
• Checking the pressure relief device’s maximum pressure rating aligns with the piping system’s limits.
• Reviewing applicable testing procedures, pressure requirements and permissible pressure drops.
• Ensuring adequate ventilation for any released gas during testing.
• Having fire extinguishers on hand along with gas detection equipment as precautions.
• Using personal protective equipment like safety goggles, gloves and closed shoes.

Undertaking these preparations helps ensure testing proceeds smoothly and safely.

Conducting the Test

To conduct a gas line pressure test safely and effectively:

1. Verify all gas appliances near the section being tested are switched off to minimise gas draw during testing.
2. Connect the pressurised air/nitrogen cylinder and gradually pressurise the isolated pipe section to 1.5-3 times the normal maximum operating pressure.
3. Close the cylinder valve once target test pressure is achieved to seal off further input.
4. Observe the test pressure gauge closely, ensuring it remains stable and does not indicate a pressure over the permissible limits throughout the entire mandated test duration, usually 10-15 minutes.
5. Stable pressure should persist, with any permissible decreases being significantly lower than tenfold of the typical 3 psi limit.
6. Mark any leaks for later repair if rapid pressure losses indicative of a high leakage rate occur.
7. Release test pressure slowly at the end of the test, being prepared to further investigate any whistling.
8. Flanges and caps get removed once testing finishes and repairs complete.

Following structured procedures ensures tests apply adequate pressure to gas lines to certify integrity.

Analyzing Results

Analysing the results of a gas line pressure test involves carefully observing the pressure gauge reading and the allowable leakage rate throughout the entire test duration. The pressure shall be less than the maximum allowable drop to remain within the acceptable range. For example, allowable leakage during the test should not exceed 3 psi over the mandated 10-15 minute timeframe.

If the gauge indicates the pressure is holding steady, it signals the gas piping has integrity. However, rapid pressure losses beyond allowed limits usually signify leaks. These require further investigation to pinpoint and repair faults before retesting.

Other acceptance criteria include an absence of whistling when pressure gets released, confirming joints are gas-tight. Safe pressure tests verify soundness before reinstating the gas supply. Failed tests mandate repairs until proving successful.

Normal Pressure Ranges

Typical home natural gas line pressures range from around 7 to 11 inches of water column, equivalent to approximately 0.25 to 0.4 psi. Allowable pressure ranges often have upper and lower limits.

In industrial and commercial settings, gas line pressures are higher, with test pressures often set between 3 to 5 psi.

All pressure testing applies substantially increased pressures, commonly 1.5 to 3 times the maximum operating pressure.

Gas pressure tests allow minor drops within permissible tolerances, usually less than 3 psi over the mandated test duration. Greater pressure losses signal faults needing repair before the system can undergo further testing to verify gas-tight integrity.

Troubleshooting Pressure Issues

Several common issues may arise during gas line pressure testing that require troubleshooting:

Identifying Leaks

Rapid pressure drops require technicians to perform a leak test on all welded and threaded joints. Leak detection fluid gets applied while pressures remain elevated. Bubbles pinpoint flaws needing fixing before retesting.

Trapped Air Pockets

Pneumatic testing can trap air pockets in the pipes, leading to gradual pressure drops as air escapes. Temporarily repressurising often resolves this before testing recommences.

Expanding Pipes

Temperature increases can cause slight gas expansion in pressurised lines, sometimes mistaken for leaks, underscoring the importance of following correct testing procedures. Cooling pipes before retesting helps gauge true pressure drops attributable to real leaks.

Faulty Gauges

Inaccurate pressure gauge readings falsely signal leaks. Interchanging with a calibrated test gauge determines whether the drops are due to actual piping issues or simply gauge inaccuracies. Consult gas fitting professionals if unsure.

Methodically assessing testing anomalies ensures sound troubleshooting. Pinpointing causes helps tailor effective repairs so retesting proves successful.

Compliance With Standards and Regulations

Adhering to plumbing codes and standards is crucial when pressure testing gas lines to ensure safety and compliance. In Australia, AS/NZS 5601.1 dictates strict procedures for testing and allowable pressure ranges. Other local regulations also apply.

Key responsibilities for plumbers and gas fitters include:

• Following the prescribed process for isolating, capping and pressurising lines.
• Employing accurately calibrated pressure gas testing equipment that meets all regulatory requirements.
• Administering test pressures ranging from 1.5 to 3 times the standard operating level of the pipelines.
• Maintaining pressures within permissible tolerances over test durations.
• Identifying and repairing any leaks or faults before retesting.
• Accurately documenting all test results for certification.
• Having current gas fitting licences from state authorities.

Improper pressure testing or non-compliance with regulations can result in severe penalties. For expert install and authorised gas line pressure tests, choose Guildford Plumbing. Visit our website or call us at 1300 349 338.