【HaiChuan Civil Engineering Discussion】What are the key inspection points for the water tightness test of concrete sewage pipes?

Specifications for pipe water tightness testing: 1. For the tightness testing of pressure-free pipes, pipe sealing bladders are primarily used. 1.1. For sewage pipes, pipes for combined sewage and rainwater systems, as well as rainwater pipes in areas with collapsible or expansive soils, a water tightness test must be conducted using the water filling method before backfilling is carried out. 1.2 The test pipe sections should be separated by well intervals, with a length not exceeding 1 km, and testing should be carried out with wells present. 1.3 During the pipe water-sealing test, the test section of the pipeline shall comply with the following requirements: 1.3.1 The visual quality of the pipeline and inspection wells has been approved ； 1.3.2 The pipes are not backfilled with soil and there is no water accumulation in the trench ； 1.3.3 All reserved holes must be sealed to prevent water leakage ； 1.3.4 The bearing capacity of the end plugs of the pipeline, as calculated, should be greater than the resultant hydrostatic pressure ； Apart from the reserved inlet and outlet pipes, it should be sealed tightly to prevent water leakage. 2. The water tightness test of pipelines shall comply with the following provisions: 2.1 When the designed head upstream of the test section does not exceed the inner wall surface at the top of the pipe, the test head shall be calculated as the inner wall surface at the top of the pipe upstream of the test section plus 2m ； 2.2 When the design head upstream of the test section exceeds the inner wall height of the pipe, the test head shall be taken as the design head upstream of the test section plus 2 meters ； 2.3 When the calculated test head is less than 10 m but has already exceeded the elevation of the upstream inspection well opening, the test head shall be based on the elevation of the upstream inspection well opening ； 2.4 The pipe water tightness test shall be carried out in accordance with the water tightness test method specified in Appendix B of this code. 2.5 During the pipeline tightness test, a visual inspection shall be carried out; there should be no leakage. The test is considered successful if it meets the following requirements ； 2.5.1 The measured water infiltration rate is less than or equal to the allowable water infiltration rate specified in Table 10.3.5 ； 2.5.2 When the inner diameter of the pipe is larger than the diameter specified in Table 10.3.5, the measured water leakage rate shall be less than or equal to the allowable water leakage rate calculated using the formula below ；

Allowable water leakage amount for pressure-free pipeline tightness test

2.5.3 The allowable seepage volume for pipes with irregular cross-sections can be calculated based on their perimeter, as if they were circular pipes. 2.6 In areas with a shortage of water sources, when the inner diameter of the pipeline is greater than 700 mm, sampling can be carried out at 1/3 of the number of well sections. Regulations for the water tightness test of pressure-free pipes in petrochemical water supply and drainage systems: 1. For sewage pipes, combined sewage and rainwater pipes, as well as rainwater pipes in areas with collapsible or expansive soils, a water tightness test using the water filling method shall be conducted to measure the leakage rate before backfilling. 2 The test pipe sections should be divided according to the well spacing, with a length preferably not exceeding 1 km, and testing should be carried out with wells present. 3 The water tightness test of the test pipe section shall be carried out after the visual quality of the pipeline and inspection wells has been approved, with no water accumulated in the trenches, and it must meet the following requirements: a) There shall be no bends that could cause water to accumulate, nor any foreign objects that could affect water flow ； b) No backfilling at the joints of concrete pipes or pipes made of other materials ； c) The ends must be securely sealed and leak-free. 4 For the pipe water tightness test, the head is calculated as the design head at the inspection well upstream (where \"upstream\" refers to the higher end of the slope) plus 2 m; if it exceeds the height of the upstream inspection well’s opening, then the height of that opening shall be used as the reference. The pipe section under inspection should be filled with water and left to soak for no less than 24 hours; under the condition of continuous water addition to maintain a constant test head, the observation period should be no less than 30 minutes, after which the leakage rate is measured. 5 During the pipeline tightness test, a visual inspection shall be carried out to ensure there is no leakage; furthermore, if the measured amount of leakage according to formula (8) is less than or equal to the allowable amount of leakage calculated using formulas (9) and (10), the tightness test is considered successful. The actual water leakage amount during the pipe water tightness test is calculated using formula (8). The allowable water leakage amount for concrete pipe water tightness tests is calculated using formula (9), while that for plastic and cast iron pipes is calculated using formula (10). 6 In areas with a shortage of water sources, and when the inner diameter of the pipeline is greater than 700 mm, a sample of 1/3 can be taken based on the number of well sections. 7 Sewer pipes that discharge highly corrosive and heavily polluted wastewater must not leak. The water-sealing test is carried out according to the following procedure: 1) After the test section is filled with water, it should be left to soak for no less than 24 hours. 2) Timing begins when the test head reaches the specified value; the amount of water seeping through the pipe is monitored. Until the end of the observation period, water must be continuously added to the test section to maintain a constant test head. The observation time for water seepage shall not be less than 30 minutes. 3) The measured seepage rate should be calculated using the following formula: q = W / (T × L), where q is the measured seepage rate, in L/(min·m); W is the amount of water added, in L ； T —— Observed time of measured seepage volume, min ； L — Length of the test section