Storm Water and Sewage Pipe Testing

Rainwater and sewage pipe inspection mainly conducts scientific testing and analysis on the pipe structural condition testing, pipe functional condition testing, pipe connection condition and ancillary facility testing, surrounding soil condition testing, flow and water quality monitoring, and pipe position and burial depth re-verification, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Pipe structural condition testing: Mainly evaluates the physical integrity of the pipe itself. The testing contents include the defects such as the pipe cracks, deformations, joint offsets, disconnections, corrosion, perforations and leakages. These defects directly affect the load-bearing capacity and service lives of the pipes, and are the key testing items of preventing the ground collapse and environmental pollution.

Pipe functional condition testing: Evaluates the conditions of the pipe conveying capacity. The emphases are on the problems reducing the water flow cross-sections such as the sedimentation, scaling, obstructions, root intrusion and water level silting in the pipes. These problems are the main causes of the poor drainage, urban waterlogging and sewage overflow.

Pipe connection condition and ancillary facility testing: Checks the sealing of the pipe joints, manhole well body structures, well cover conditions, branch pipe connections and the special pipe sections such as the inverted siphons. The joint leakages are the main channels of the groundwater infiltration and sewage exfiltration, directly affecting the operation loads and efficiencies of the sewage treatment plants.

Surrounding soil condition testing: Probes whether there are the geological defects such as the voids, looseness and soil loss around the pipes. These defects are usually formed by the long-term leakage and scouring of the pipes, and are the major safety hazards causing the road subsidence. The technologies such as the ground penetrating radar need to be used for the detection.

Flow and water quality monitoring: Through the installation of the equipment such as the flow meters and water quality online analysers, the flow rates, flow velocities, fullness degrees and key water quality parameters (such as the pH, COD, ammonia nitrogen and suspended solids) in the pipes are monitored. This monitoring is used to evaluate the system operation loads, analyse the infiltration and inflow conditions, and investigate the abnormal discharge sources.

Pipe position and burial depth re-verification: The technologies such as the ground penetrating radar and pipe detectors are used to precisely determine the plane positions, directions, burial depths and diameters of the underground pipes. This provides the accurate surveying and mapping data basis for the pipe repair, renovation and surrounding engineering construction, avoiding the construction damages.

Testing Scope

Municipal public drainage pipe network: Covering the rainwater pipes, sewage pipes and combined pipes under the urban main roads, secondary roads and branch roads. This is the aorta of the urban drainage system, with the highest testing priority, and is usually organized and implemented periodically by the municipal drainage management departments.

Internal pipe networks of the residential areas and enterprises and institutions: Including the rainwater and sewage pipes within the boundary lines of the residential areas, commercial areas, industrial parks, schools and hospitals, etc. This type of pipe network is the "last kilometer" connecting the users and the municipal pipe network, and its conditions directly affect the user drainage experience and the regional system efficiencies.

Pipe networks in the construction-affected and geological risk areas: Targeting the pipes within the influence ranges of the major engineering constructions such as the subways, tunnels and deep foundation pits, as well as the pipes below the areas with the poor geological conditions and the collapse occurred areas. The special testing and monitoring before, during and after the construction need to be carried out, to evaluate the risks and take the protection measures.

Old pipe networks and disease-prone pipe sections: Targeting the pipe sections with the pipe ages exceeding the design service lives, backward materials (such as the brick masonry and concrete pipes), as well as the pipe sections historically recorded with the defects or repeated blockage and overflow problems. This type of pipe network is the top priority of the testing and repair plans.

Rainwater and sewage mixed connection and wrong connection investigation: In the rainwater and sewage separation renovation areas, whether the sewage is mixed into the rainwater pipe network and whether the rainwater is connected into the sewage pipe network need to be systematically tested. This scope of testing is usually carried out simultaneously with the water quality monitoring and pipe endoscope testing.

Pumping station and sewage treatment plant inlet and outlet pipelines: The key inlet and outlet water pipes connecting the pumping stations and sewage treatment plants are inspected. The health conditions of these pipelines are directly related to the pumping station operation safety and the inlet water stability of the sewage treatment plants, and the testing standards are usually more stringent.

Testing Methods

Closed-circuit television testing method: It is the most widely applied and intuitive pipe endoscope testing method at present. The crawlers carry the high-definition cameras to walk inside the pipes, recording and transmitting the pipe internal images in real time. The technical personnel locate, qualitatively and quantitatively analyse the defects according to the video data, and generate the detailed inspection reports.

Sonar testing method: Mainly applied to the water-filled pipes, especially the detection of the underwater sedimentation conditions. The system transmits the sound waves to the pipe walls through the sonar probes and receives the echoes, forming the pipe cross-section profile images through the processing, and can precisely measure the thicknesses, distributions and estimated volumes of the sediments.

Pipe periscope (QV) testing method: A fast preliminary screening method. The camera rods equipped with the strong light sources and zoom lenses are extended into the manholes for the visual inspection of the pipe interior parts. This method is fast and low-cost, suitable for the preliminary investigation, emergency investigation of the pipe conditions or the re-verification of the specific problems after the QV testing.

Pipe scanning and assessment technology: Integrating the multiple sensors, while the CCTV testing, through the laser scanning or structured light scanning technologies, the high-precision three-dimensional point cloud models of the pipe interiors are obtained. The pipe deformations, corrosion depths and sedimentation amounts can be precisely measured, providing the precise data for the trenchless repair design.

Smoke testing and dye testing: Used to find the pipe leakage points, illegal connections and manhole connectivity. The smoke testing releases the harmless smoke into the pipes and observes the ground smoke points; the dye testing puts the tracer dyes into the suspected sources and observes the outlet water colours downstream. Both are the traditional but effective auxiliary testing means.

Ground penetrating radar and electronic marker positioning method: The ground penetrating radar is used to non-destructively detect the soil voids and loose areas around the pipes from the ground surface; the electronic markers are buried at the pipe crowns during the pipe repair or new construction, and later the pipe positions and burial depths can be precisely positioned with the dedicated detectors, avoiding the excavation investigations.

Testing Standards

Domestic Standards:

1. CJJ 181, Technical specification for detection and evaluation of urban sewer pipeline

2. GB 50268, Code for construction and acceptance of water and sewerage pipeline works

3. CJJ 6, Technical specification for safety of maintenance of urban sewerage pipelines

International Standards:

1. EN 13508-2, Condition of drain and sewer systems externally and internally — Part 2: Coding system for visual inspection

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Pipe closed-circuit television (CCTV) inspection system: The core equipment includes the crawlers (wheel type and crawler type), high-definition waterproof underwater cameras, control cable reels, master control computers and analysis software. The high-end systems have the functions such as the laser ranging, sonar integration and three-dimensional modeling, which can meet the inspection needs of the different pipe diameters, water levels and lengths.

Pipe sonar inspection system: Composed of the sonar probes (transducers), control units, display and recording equipment and positioning encoders. The probes are dragged at the uniform speeds in the pipes for the 360-degree scanning. This system has no requirements for the lighting and transparency of the detection environments, and is the necessary equipment for evaluating the underwater sedimentation conditions of the pipes.

Pipe fast inspection equipment: Mainly referring to the pipe periscopes. The equipment is light and portable, usually composed of the camera rods, high-intensity light sources, controllers and displays. Some advanced models have the laser ranging and wireless image transmission functions, greatly improving the efficiency and convenience of the field operations.

Pipe quantitative inspection system: Such as the laser profile scanners and structured light scanners. They are installed on the CCTV crawlers, emitting the laser lines or gratings to the pipe walls, capturing the deformed images through the cameras, and generating the cross-section deformation curves with the precise dimensions and three-dimensional models through the software processing.

Auxiliary cleaning, dredging and inspection equipment: Including the high-pressure cleaning trucks, combined dredging trucks and grab trucks, etc. Before the testing, the necessary desilting and dredging of the pipes usually need to be carried out, ensuring that the inspection equipment can pass smoothly and obtain the inspection images. These equipment are the prerequisites for guaranteeing the smooth development of the inspection work.

Positioning and surveying and mapping instruments: Including the pipe detectors, ground penetrating radars, total stations and GPS receivers, etc. Used to precisely detect and calibrate the spatial positions (X, Y, Z coordinates) of the underground pipelines from the ground surface, and correspond the detected defect points with the spatial positions one by one, establishing the complete pipe network geographic information system database.