We firmly believe that there are no better materials available to rehabilitate sewer/water lines than polyethylene for pipe bursting and using polyethylene piping in all pipe bursting and sliplining applications.
High density polyethylene (HDPE) have been the most used replacement pipes for pipe bursting applications The main advantages of PE pipe are its continuity, flexibility and versatility. The continuity is obtained by hot fusing long segments together in the field during the installation, which reduces the possibility of stopping the process. The flexibility allows bending the pipe for angled insertion in the field. In addition, it is a versatile material that meets all the other requirements for gas, water and wastewater lines. Due to its high abrasion resistance, thick walls and relative toughness make polyethylene pipes eminently suitable for even slurry pipelines.
ICI engineers in the UK discovered polyethylene in 1933. Field experience of more than 78 years can therefore substantiate a life expectancy of more than 100 years for non-pressure sewer lines.
Polyethylene is, in chemical terms, a non-polar high molecular weight paraffin of the hydrocarbon family. Hence, it is very resistant to strong acids, strong bases and salts. It is only mildly affected by aliphatic solvents although aromatic and chlorinated solvents will cause some swelling.
Polyethylene is also not subject to biological attack through the action of micro-organisms such as bacteria, fungi or spores. It is insoluble and does not swell or degrade in most commonly used fluids. Consequently, it cannot be joined using solvents, “cements” or common adhesives. However, it can easily be fused or welded.
It is exactly this last-mentioned characteristic that makes polyethylene such an ideal material for sewer and water lines. Pipes that have been properly welded together by the butt weld or the fusion weld process will be perfectly watertight and there will be no chance for water or tree roots to enter the continuously welded polyethylene system.
S.P. Miller, a Charted Civil Engineer at Industrial Pipe Systems Pty Ltd, compared the flow rates of various types of pipeline materials, i.e. cement lined cast iron, PVC and MDPE. He used the Hazen-Williams formula as a check and also applied the Colebrook-White formula to determine the flow rates. The Engineers of the Sydney Water Board have used the Hazen-Williams formula successfully for many years. Their design procedure has been supported by many field tests and hydraulic gradient reviews.
The comparison for equivalent internal diameter pipelines proved the polyethylene pipes to be superior to PVC and PVC in its turn to be superior to cement lined cast iron pipes.
It is reiterated that with the pipe bursting and slip-lining methods that are used by PRS, the junctions of house connections to the main sewer/water line are completely replaced. For most lines, a saddle is welded onto the new water main and the rest of the house connection rehabilitated to an agreed point. PRS uses high quality polyethylene piping and fittings. Future extensions or other work on the line can therefore be done by any person trained in the use of polyethylene. Equipment to do fusion and butt-welding can be hired from local plumbing suppliers, i.e. Reece Plumbing.