Sewerage and drainage

The use of plastics pipes for both pressure and gravity sewers is extensive in North America, Europe and Australia. In addition there is rapid growth in the use of plastics liners for repair of old and leaking sewer installations.

Availability of large diameter plastics pipes at competitive prices gives design engineers an opportunity to select products on cost and performance basis. Long life expectancy, low maintenance requirements are major advantages in the use of plastics pipes for sewage and drainage applications.

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Case Studies

Logan City Council installed more than 1.6km of Vinidex 375mm diameter Ultra-Rib trunk sewer line. The optimised profile design of Ultra-Rib offered several time saving advantages for the contractors. Supplied in 3m lengths, the 375mm pipe was easily manhandled on site even on the tight constraint of trench shoring in the 5.5m deep trenches. Cutting by hand saw or abrasive disc is quick, simple and the end does not require chamfering.

The rubber sealing ring sits between the radial ribs on the outside of the pipe and cannot be dislodged during installation. Jointing was easily achieved by hand pushing with a bar and wooden block. Included in the installation were three road crossings requiring tunnel boring to minimise traffic disruption. Ultra-Rib was run through 600mm diameter steel pipe as a conduit and three timbers were strapped to the PVC pipe to prevent floating and to support during grouting. PVC’s superior flow characteristics became vital during the installation of one 90m section of the line that had to be laid on a flat grade of one in 1500 to pass under existing water and storm water pipes.

Australia’s largest coastal lake system, Lake Macquarie, is strategically located between Sydney and Newcastle. Large parts of the area were relying on septic tanks and as development increases, the threat to the water quality due to leaching grows. Conversion to an efficient gravity sewer became essential to protect the fragile environment. As part of a major 10 year long Hunter Sewerage Project, the NSW Public Works Department has replaced septic systems with fully piped sewer schemes and treatment works. For the last stage, at Bonnells Bay West near the lake, a combination of Iplex uPVC and HOBAS GRP sewer pipes have provided an ideal system.

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Solid wall (SN4) class uPVC pipe was also chosen for the performance of the rubber ring joints, ensuring root and infiltration does not compromise sewer integrity. Iplex was able to supply the whole range of diameters required from 100mm to 375mm uPVC, to AS1260 and HOBAS 450mm to 900mm, SN 10,000 to AS3571 with all associated fittings. The comparatively light weight and ease of handling of both uPVC and Hobas provided a further cost advantage during installation saving contractors, considerable time and labour. The pipes will provide efficient service, resist corrosion and scum buildup, and ensure excellent long-term flow rates. Homes in Bonnells Bay West will be connected to a highly efficient gravity fed sewer. The Hunter project will continue to link areas to the system ensuring that the environment is protected and that people can enjoy this beautiful area in years to come.

Coe Drilling Australia and trenchless technology. Brisbane City Council working with Brisbane Water instigated a sewer project which includes 12.5 km of new pipeline, three new pump stations and upgrade to 4 existing pump stations. The HDD Brisbane River Crossing part of the project was awarded to Coe Drilling Australia to install 762 m of DN 400 HDPE 100 PN 20 pipe. Using Horizontal Directional Drilling technique, the task of drilling and installing the pipeline was completed in August 2004. The polyethylene pipe was welded and tested by Leightons, the major contractor, on the north side of the river. Once all pilot hole, hole openings and hole conditioning had been completed, the rig was mobilised to the south side for the pipeline installation. This operation allowed the pipeline to be pulled through the longer open section of gravels before entering the basalt bedrock and back up through a shorter section of gravel on the south side.

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The previous year Coe had completed a project for Sydney Water, an inclined sewer borehole to intercept a sewer carrier tunnel at Hazelbrook NSW. drilling through Hawksbury sandstone to install a DN 400 HDPE 100 PN20 pipe, 375 m in length.

PE for Hunter Water Sewer Project: Hunter Water Corporation installed a DN900 Polyethylene pipe (PE) in a record breaking 900m directional drill at Burwood Beach south of Newcastle in NSW. The pipeline directs waste water to the Burwood Beach Treatment Plant.

Go to the Polyethylene for Hunter Water Sewer Scheme paper for details.