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MDPE, HDPE, HPPE - Polyethylene Pipe and FIttings
Polyethylene (PE) is a very robust and ductile pipe material. In its early days it was often referred to as "Alkathene", which was, in today's parlance, MDPE or Medium Density Poly-Ethylene. Although MDPE is still used for some smaller bore pipe systems, larger bore systems are HDPE (High Density Polyethylene).
PE pipe tends to come in three main colours;
- Blue - Approved for potable water systems
- Black - Used for non-potable systems
- Yellow - Used for gas, yellow PE pipe is, unlike standard PE, not gas permeable and is manufactured with a special lining.
We primarily supply black PE systems comprising of pipe, electrofusion and long spigot fittings. We also supply small bore blue MDPE pipe from stock, and can provide quotations for larger bore blue polyethylene pipe and fittings if required.
We do not supply yellow gas PE pipe and fittings.
Polyethylene cannot be glued or solvent welded (like PVC and ABS pipe). The jointing methods therefore need to either rely on mechanical or heat welded methods.
| Jointing Method | |
|---|---|
| Compression Jointing | Compression couplings incorporate a grip ring that holds the pipe firm once it has been pushed through an O-Ring. A compression ring is then turned, which tightens the grip. Compression fittings are usually made from Polypropylene (PP) with an EPDM O-Ring, although some metal fittings are occasionally used. Compression fittings can be installed by non-skilled persons without the need for special tools or equipment. |
| Electrofusion Jointing | Electrofusion fittings (also called EF) have a copper coil wound through the inside of the fitting. The pipes are pushed into either side of the fitting and an electric current passed through the coil. The current heats the copper coil and melts the two surfaces together. |
| Butt Welding | Butt welding uses specialist hydraulic clamping machinery to trim the ends of two pipes perfectly flat. A heat plate is then placed between the ends and after they have been heated for a preset period, the plate is removed and the machinery pushes the two ends together, causing them to melt into each other. A raised "bead" is formed as a result of the joint, running around the inside and outside of the join. This can cause issues if a smooth internal bore is required. Machinery can be used to remove the bead, but this adds another complication to the process. Butt welding is most commonly used on larger pipe bores, where the cost or availability of EF fittings prohibits their use. |