Test procedures for pressure and gravity pipes and maintenance structures

Hydrostatic test all pressure mains after trench filling and compaction and after all thrust restraining concrete have cured for at least three days. For large land subdivision developments, all lot connections must be included in the test. Water for testing must be clean, potable quality water, obtained from the existing mains supply.

The pressure test must be a minimum of 1050 kPa for mains up to DN300. Mains equal or greater than DN375 must be a minimum of 1200 kPa. Loss of pressure greater than 50 kPa results in failure of test. Shorten the length of pipeline to test where practical or if significant changes in elevation affect test pressure.

Adopt a maximum test length of 1000 m. If practically beneficial, the certifying consultant can test the mains in sections. A water and sewer infrastructure plan to track sections of mains tested is recommended. Pressure and chlorination testing can be combined to reduce time taken for commissioning.

The contractor is permitted to hydrostatically test against existing valves after the valve is closed and locked by Power and Water personnel. Power and Water cannot guarantee the condition of existing valves and that they will hold pressure during test.

A blanking plate or spade between flanges is also acceptable, provided that there is adequate lateral restraint in the immediate area to prevent dislodging of socketed pipe fittings. Based on site conditions, the spade specification (thickness and material) must be provided by the certifying consultant.

Where no valve exists or at an end cap, Power and Water may install a valve with a puddle flange thrust block at the developer’s expense to provide isolation between new and existing mains.

Pressure testing polyethylene (PE) pipes requires special processes as they may continue to expand significantly throughout the test period. When a PE pipe is sealed under a test pressure there may be decay, even in a leak free system, due to the creep response and stress relaxation of the PE material. Due to this behaviour, standard pipe testing may not be suitable for PE pipes. Testing of PE mains and services must be tested separately from all other pressure mains of different material and as per WSA 01-2004 Polyethylene Pipeline Code Version 3.1.

Test procedure

1.Prior to setting test pressure, allow a minimum of 24 hours for the test water temperature to stabilise and dissolved air to vent from the system. Fill cement-lined pipes 24 hours prior to testing to allow for lining saturation. Clean the section and then slowly fill it with water, ensuring that air has been completely expelled.

2. Use a test rig that has two calibrated pressure gauges. Each gauge must have a range of 0 – 2500 kPa and must have a current calibration certificate within six months of test date. Both gauges must read within 5% of each other. Use the gauge recording the lower of the two readings.

3. Pressurise the line to 75% of the test pressure and leave for a minimum of 12 hours. The preliminary pressurisation is intended to:

• stabilise the main by allowing most of the time-dependent movement to occur
• achieve saturation in absorbent materials; and
• allow pressure-dependent increase in volume of flexible pipes prior to the main test.

4. Provided there are no obvious leaks in the main, steadily raise the pressure in the main until the specified test pressure is reached. Maintain the test pressure for four hours. Measure and record the pressure reading at half hour intervals. Visually inspect the line for leaks. Loss of pressure greater than 50 kPa results in failure of test. If a leak is suspected but is not visible, the certifying consultant can consider the use electronic assistance.

5.Accept the pressure test on a section of main if:

• there is no failure of any thrust block, anchor block, pipe, fitting, valve, joint or any other pipeline component
• there is no visible leakage
• the measured loss rate for the relevant test period of the pressure testing does not exceed the maximum allowable loss rate as determined above.

6 .If any of the tests prove to be unsatisfactory, detect and rectify the fault and re-test. Continue to rectify and retest until a satisfactory test result is achieved. Even if testing produces satisfactory results, rectify any main or conduit in which there is a visible or detectable leak or blockage.

7. Flush and dispose of test water in accordance with the certifying consultant’s recommendation.

Test procedure

1.Test to 1050 kPa of pressure after physical completion of new water service.

2. A satisfactory test is where there is no drop in pressure or loss of water after minimum 30 minutes.

3. If required, locate and repair all leaks and retest in accordance with the procedures of this clause.

Test procedure

1.Air test each welded joint at 70kPa with the certifying consultant and Power and Water representative present, as soon as possible after completion of the joint with dry air and before backfilling.

2. Apply a soapy water solution to the joint welds and inspect visually for leaks. Repair faulty weld and retest to satisfaction of the certifying consultant.

3. Pressurise overlapped area between welds using the tapped hole provided.

4. On satisfactory completion of the test, seal the tapped hole by seal welding and grinding flush or sealing with a hexagonal head plug and approved jointing compound.

Vacuum air test of sewer MH as per test procedure below is Power and Water’s preferred test method. Test all MHs after the backfill is placed and compacted.

Where the certifying consultant permits hydrostatic testing as an alternative to vacuum testing, the hydrostatic testing of all MHs must be carried in accordance with the following requirements below.

All MHs must be tested.

Test procedure - vacuum air test

1. Apply an initial test vacuum pressure (negative pressure) of approximately 37 kPa to the top of the MH. Close the valve on the vacuum line and shut off the vacuum pump. Allow the air pressure to stabilise for at least three minutes to identify any initial leakage.

2. When the pressure has stabilised, allow the gauge pressure to drop and commence time recording when pressure reaches 34 kPa. Record the time for the pressure to drop to 30 kPa.

3. Accept the MH under test if the time for the vacuum reading to drop from 34 kPa to 30 kPa meets or exceeds the relevant time in the table below.

4. If the time is less than the minimum specified the table below, re-apply the vacuum to identify any leaks. Rectify all defects prior to conducting any further testing. Rectify any visible or audible faults even if the vacuum testing is satisfactory.

Vacuum test - Minimum time intervals for pressure drop

Note: Times of intermediate diameters and depths may be interpolated

Test procedure - hydrostatic test

1. Hydrostatic testing of MHs will be undertaken by plugging all pipe openings in the walls and by filling the MHs with water to the top of the access cover surround. The plugs must be positioned in the pipes as near as practicable to the internal face of the maintenance structure.

2. After allowing a minimum of 30 minutes for absorption, the MH must be refilled and the loss of water during the following 30 minutes measured.

3. The test on the MH will be considered satisfactory provided that there is no visible water loss. The plug of the outlet must be fitted with a suitable release for emptying the MH on satisfactory completion of the test.

Sewer gravity mains can be either air (low pressure or vacuum) or hydrostatically tested as per the test procedures below. The certifying consultant must determine the preferred method of testing.

The sewer gravity mains must be tested after the entire area with all other services is installed, and has been completed to finished surface. It is recommended that large sewer mains (≥ DN750) be inspected and tested during construction and before the construction of MHs.

All new sewer pipelines and sanitary drainage and other non-pressure installations must be tested. The tests are to include external drops, property connections, vertical risers, inspection fittings and maintenance shafts.

The tests must also be applied to any section of existing pipeline or drain that has been repaired or replaced. Complete all pipework including house drain connections and seal open ends (permanently where specified) before commencing test. Plug pipeline ends tightly and leave joints exposed.

Test procedure - low pressure air test

1. Plug all sewer inlets and outlets and cap and seal all maintenance shafts, inspection opening shafts and risers in the test length of sewer. Extra care must be considered as movement in the rubber ring joints on risers may occur.

2. Slowly apply an initial test pressure of approximately 27 kPa.  Rapid pressurisation can cause significant air temperature changes that may affect testing accuracy. Close the valve on the air pressure line and shut off the pump. Allow the air pressure to stabilise for at least three minutes to identify any initial leakage.

3. When the pressure has stabilised, allow the gauge pressure to drop and commence time recording when pressure reaches 24 kPa. Record the time over the test period specified in the table below.

4. Accept the length of sewer under test if the test pressure loss is less than 7 kPa for the relevant time interval specified in the table below.

5. If the sewer fails the test, re-apply the pressure to identify any leaks. Rectify all defects prior to conducting any further testing. Rectify any visible or audible faults even if the pressure testing is satisfactory.

Test procedure - Vacuum air test

1. Plug all sewer inlets and outlets and cap and seal all maintenance shafts, inspection opening shafts and risers in the test length of sewer.

2. Apply an initial test vacuum pressure (negative pressure) of approximately 27 kPa. Close the valve on the vacuum line and shut off the vacuum pump. Allow the air pressure to stabilise for at least three minutes to identify any initial leakage.

3. When the pressure has stabilised, allow the gauge pressure to drop and commence time recording when pressure reaches 24 kPa. Record the time over the test period specified in the table below.

4. Accept the length of sewer under test if the test vacuum loss is less than 7 kPa for the relevant time interval specified in the table below.

5. If the sewer fails the test, re-apply the vacuum to identify any leaks. Rectify all defects prior to conducting any further testing. Rectify any visible or audible faults even if the vacuum testing is satisfactory.

Notes: Timing of the test duration to commence after the three minute initial period.

Test duration times for other combinations of pipe size and test length to be interpolated.

Test procedure - hydrostatic test

1. Fill the pipeline section with water and apply a test pressure head:  a. not less than two metres above pipe obvert or ground water level at the upstream end b. not greater than six meters above pipe obvert at the downstream end.

2. Where the pipeline gradient of the test length is too steep to achieve the pressure head requirements, shorten the pipeline test length.

3. Fill the pipeline slowly to the required head and bleed air from behind upstream plugs. For vitrified clay (VC) and reinforced concrete (RC) pipes and cement mortar lined pipe, let the pipeline stand for at least two hours to saturate the pipe walls.

4. Mark water level at the start of the test.

5. During pressuring, check for leakage from plugs and any test apparatus.  Where leakage occurs, release the water, make the necessary repairs and adjustments and re-fill.

6. Read just to the test pressure head and commence monitoring the loss of water for a test period of 30 minutes.

7. The test is not accepted if there is loss of water.

8. Re-apply the test pressure head and check the pipeline for leaks. Repair leaks to the satisfaction of the certifying consultant and retest.

Visually inspect all plastics-lined concrete MHs for defects such as cuts, tears, or cracks and open or incompletely fused thermoplastic lining welds.

Reject linings with visible projections or depressions that exceed 25 mm depth measured perpendicularly to the plastics lined surface.

Probe all field welds of thermoplastic lining with a feeler gauge to determine all defective welds requiring re-welding i.e. weak welds and welds where the probe enters more than 3 mm.

Mark all defects with chalk or a spirit pen with colour contrasting with the coating or lining.

Repair all visible and weld defects in accordance with the manufacturer’s printed instructions using qualified welders and authorised methods.

After repair or visible and weld defects, undertake spark testing to detect discontinuities in accordance with Clause 7 of AS 3894.1. Use equipment calibrated to 20,000 V within the last 12 months in accordance with Appendix C of AS 3894.1.

Test procedure

1. Allow 20 minutes inclusive of warm-up for the spark testing equipment to reach equilibrium conditions. Ensure the surface of the lining is dry. Adjust the voltage of the spark testing equipment to a minimum of 12,000 V (but no more than 13,000 V) and secure an earth connection to the underlying substrate.

2. Pass the brush electrode of the spark testing equipment over the lining at a rate of not greater than 0.3 m/s, maintaining contact between the electrode and the test area and using an appropriate motion.

3. Where the instrument indicates a discontinuity, determine the exact location of the discontinuity (do not hold electrode stationary against the surface) and clearly identify it on the test surface with the marker.

4. Continue testing until the entire coating or lining has been tested.

5. Undertake repair of discontinuities in accordance with the manufacturer’s printed procedures. Repeat spark testing and repair cycle until there are no discontinuities detected.

6. If overheating during repairs causes any charring of thermoplastic welds, replace all charred sections in accordance with the manufacturer’s printed procedures.