Field Testing

The types of field testing require for various sewer pipelines are summarised in Tables 9.1. Details of the testing requirements and constraints shall be referred to MSIG Volume 3.

Table 9.1: Summary of Field Testing for Sewer Pipelines

Pipeline System Type of Test

Test for straightness and grade:

- Laser beam with sighting targets;

- Sight rails and boning rod;

- Lamp and mirror;

- Insertion of a smooth ball.

Exfiltration test:

- Hydrostatic test - Low pressure air test Infiltration test

Deflection test Gravity Sewer

CCTV Inspection

Test for straightness, obstruction and grade:

- Same as recommended for gravity sewer.

Exfiltration test:

- Same as recommended for gravity sewer.

High pressure water test High pressure leakage test Pressure Sewer

CCTV Inspection

Check the SDR of the pipe before installation (SDR is the thickness to diameter ratio of the pipe).

Vacuum Sewer

Vacuum test.

9.2.1 General Pipeline Testing Guide

The following guides are generally applicable to all water, air and vacuum tests.

• The testing should be conducted before and after the backfilling of the trench.

• The pipeline must be cleaned and cleared of obstruction before the test is conducted.

• All plugs must be installed securely.

• Concrete thrust blocks must be completed and cured before the test.

• If solvent welding is used, the joint must be cured for at least 24 hours before testing.

• Air test is easier to apply but results can be affected by small changes in temperature.

• Water test is less stringent than air test but it suffers from the disadvantage of providing and disposing of large quantities of water.

• If the pressure drop is above that allowable limit on air testing, it is recommended to conduct water test to confirm the result.

• All air and vacuum testing of pipes shall be carried under the shade away from direct sunlight to avoid temperature effects on the pipe.

• Do not over-pressurise the pipelines to prevent sudden expulsion of a poorly installed plug.

Brief description on the procedures and requirements of the testing are given below. Detailed information of the testing can be obtained from MSIG Volume 3 and relevant standards.

9.2.2 Test for Straightness, Obstruction and Grade

For gravity sewers and pressure sewers, the grade and straightness are important to achieve the design velocity. The laser beam with sighting targets and sight rails and boning rod methods will provide more exact assurance for both the grade and straightness, which shall be used whenever possible.

The lamp and mirror and insertion of smooth ball methods will provide a rough idea on whether the sewers are laid graded or straight, which should be used only for a quick check.

9.2.3 Low Pressure Air Test

The procedure of low pressure air test shall be as follows:

a. Pump in air slowly until a pressure of 25 +5,-0 kPa is reached. Where the pipeline is below the water table this pressure shall be increased to achieve a differential pressure of 25 kPa. In no circumstances should the actual pressure exceed 50 kPa.

b. Maintain the pressure for at least 3.0 min.

c. Where no leaks are detected, shut off the air supply

d. Where the pipeline fails the test, repressurised to 25 +5,-0 kPa and check for leaks by pouring a concentrated solution of soft soap and water over accessible joints and fittings.

The test length shall be acceptable, where the pressure drops by 7kPa, or less, over the required test period.

9.2.4 Hydrostatic Test

The procedure of hydrostatic test shall be as follows:

a. The test pressure shall be not less than 20 kPa, or 20kPa above the ground water pressure at the pipe soffit at its highest point, whichever is the greater, and not exceed 60 kPa at the lowest point of the section.

b. Steeply graded pipelines shall be tested in stages where the maximum pressure, as stated above, will be exceeded if the whole section is tested in one length.

c. The pressure shall be maintained for at least 2 hrs by adding measured volumes of water where necessary.

d. Any visible leaks detected shall be repaired and the pipeline shall be retested.

The test length shall be acceptable, where the addition of make-up water shall be 0.5 L/hour per metre length per metre diameter.

9.2.5 High Pressure Water Test

The procedure of high pressure water test shall be as follows:

a. Close all valves apart from the test pump input and pressurized the test length to the specified test pressure or 1.5 times the design operating pressure;

b. Apply and then maintain the test pressure by the addition of measured and recorded quantities of make-up water at regular intervals over a period, within the range of 1 hr to 12 hr;

c. Where pressure measurements are not made at the lowest part of the test length, make an allowance for the static head, between the lowest point of the pipeline and the point of measurement, to ensure that the test pressure is not exceeded at the lowest point.

There must be a drop in test pressure during the pressurised filling and in the next 10 minutes after the required pressure is achieved.

9.2.6 High Pressure Leakage Test

The test is normally conducted immediately after the high-pressure water test, i.e. before the water is drained out. The test pressure mentioned in high water pressure test must be maintained for 24 hours. The measure the amount of additional fill water requires to maintain the test pressure. The measured amount must not exceed 0.1 litre per millimetre of pipe diameter per kilometre of pipe per day for each 3 bars of pressure applied. Also check for visible leakage. The typical field pressure test equipment in AS/NZS 2566.2:2002 shown in Figure 9.1 below is recommended for adoption:

Figure 9.1: Typical Field Pressure Test Equipment Layout

9.2.7 Vacuum Test

The procedures of vacuum test shall be as follows:

a. Apply a vacuum until a negative pressure of 25kPa to 30kPa is achieved.

b. Maintain the vacuum for at least 3.0 min.

c. Where no leaks are detected, isolate the test section from the vacuum pump.

d. Where the pipeline fails the test, reapply the vacuum and check for leaks. Pouring water over joints and fittings will improve the possibility of leaks detectable by auditory methods.

The test length shall be acceptable, where the vacuum drops by 7kPa, or less, over the test period.

9.2.8 Infiltration Test

The pipeline shall be observed for infiltration over a 24 hr period, or as appropriate. In all cases where infiltration is observed, the source shall be investigated, and any leak detected shall be repaired.

This method is applicable where a freestanding water table exists at a level of at least 1.5m above the test section and 150mm above any sideline connections.

9.2.9 CCTV Inspection

Inspection by CCTV shall in accordance to the procedures:-1. Coverage

a. Initial CCTV testing & inspection shall be conducted for a minimum 10% random selection of sewer pipeline in accordance with standard procedure.

b. If the mandatory requirement of clause 9.2.9-2 is less then 5% of the entire development area, the minimum CCTV testing & inspection is 10% as in 9.2.9-1a. If the mandatory requirement of clause 9.2.9-2 is more than 5%, the minimum CCTV testing & inspection shall have an additional of 10%.

c. All new sewer pipeline shall undergo the CCTV inspection except:

i) Development with sewer length < 500m long with no interval.

ii) Vacuum sewer.

iii) Existing network to be taken over by SSD under the concessionaire agreement.

d. Prior to taking over existing network that has been approved from any owner or after rehabilitation works have been completed.