Ground Civil

Land Development Requirements

Sewer Gravity main Air 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 the test. Plug pipeline ends tightly and leaves 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 the sewer. Extra care must be considered as a movement in the rubber ring joints on risers may occur.

2. Slowly apply an initial test pressure of approximately 27.59 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.

Pipe size DN

Test lengths (metres)

 

50

100

150

200

250

300

Minimum test duration (minutes)

150

3

3

3

5

6

6

225

4

5

8

10

13

15

300

6

9

14

18

23

29

375

7

14

22

29

36

43

450

10

21

31

41

52

66

525

14

28

42

56

70

86

600

18

37

55

73

92

106

675

23

46

70

93

116

144

750

29

57

86

115

143

168

900

41

83

124

165

207

243

1000

51

102

153

204

255

300

1050

56

112

169

225

281

319

1200

73

147

220

294

367

460

1500

115

230

344

459

574

700

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

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 a 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.

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