Leakage testing is carried out to identify installation faults and sources of infiltration and exfiltration in pipelines which are required to be water tight such as sewerage systems. Leakage testing is generally not required for stormwater drains.
It is advisable to begin testing early in the pipeline installation to confirm adequacy of laying procedures and, where appropriate, to increase the length tested progressively as experience is gained.
AS/NZS 2566.2 specifies detailed procedures for leakage testing using hydrostatic testing, air or vacuum testing or infiltration testing of non pressure pipelines. These methods are summarised below. Notwithstanding this, leakage testing should be carried out in accordance with local authority requirements.
Method 1: Hydrostatic Test
Fill the pipeline with water and pressurise to not less than 20 kPa at the highest point of the section being tested, but not greater than 60 kPa at the lowest point of the test section. Maintain the test pressure for at least 2 hours by adding measured volumes of water if required. Each joint should be carefully examined visually for leaks, and any defects should be repaired. The pipeline section is deemed satisfactory if the make-up volume is less that 0.5L per hour per metre length per metre diameter. After any repairs, the pipeline should be re-tested.
Method 2: Air Test
Introduce air slowly by suitable means until a pressure of 25 kPa is obtained. Maintain for a period of at least 3 minutes. If no leaks are observed after 3 minutes, shut off the air supply. If the pressure of air contained in the pipes under test does not fall below 18 kPa within the time period specified in the Table below, the pipeline shall be considered satisfactory.
If, however, the pressure is not maintained within the specified limits, reintroduce the air and examine the pipeline for leaks by pouring a concentrated solution of soft soap and water over the joints and fittings. Identify and repair any leaks. After any repairs, the pipeline should be re-tested.
Method 3: Vacuum Test
Apply a vacuum until a negative pressure of 25 kPa is obtained. Maintain for a period of at least 3 minutes. If no leaks are observed after 3 minutes, isolate the test section from the vacuum pump. Monitor the pressure for the time specified in the Table below. If the vacuum does not drop below 18 kPa within the specified time period, the pipeline shall be considered satisfactory. Where the pipeline section fails the test, re-apply the vacuum and examine the pipeline for leaks. Identify and repair any leaks. After any repairs, the pipeline should be re-tested.
Minimum Time Intervals for 7 kPa Pressure Change in Air and Vacuum Test
|DN||Test Length -50 (m)||Test Length
|Minimum Test Duration (min)||Minimum Test Duration (min)||Minimum Test Duration (min)||Minimum Test Duration (min)||Minimum Test Duration (min)|
Method 4: Infiltration Test
Where there is a free standing water table at a height of at least 1.5m above the test section, an infiltration test can be carried out. Observe the pipe for 24 hours. Where infiltration is detected, the leak should be identified and repaired.