Polyethylene Pipe Jointing Methods: Compression, Butt Fusion, Electrofusion and Flange

There are four main ways to join polyethylene pipe, and the choice between them depends on diameter, type of line, access to a machine and whether the joint must be opened again later or stay permanent. A compression joint is fitted without a machine or power and can be opened. Butt fusion makes two pipe ends one piece with heat. Electrofusion works with a fitting that has a heating wire. And a flange joint takes the pipe to valves, pumps and metal equipment.

In this guide we compare all four with the diameter range recorded for them in our catalogue rows and give a guide to choosing. If you want the step-by-step fitting of each joint, see the article on how to connect polyethylene pipe; this article focuses on comparison and choice.

• How to connect polyethylene pipe
• Polyethylene fittings guide: compression, butt fusion, electrofusion

A polypropylene compression fitting, with body, nut, grip ring and sealing ring, holds the pipe without welding. In our catalogue compression fittings run from 20 to 125 mm, and the equal compression coupling is recorded in the PN 10 class (10 bar). These fittings are listed to ISO 17885.

The main advantage is quick hand fitting with no power, and that it can be opened and used again; for this reason it is very common on irrigation networks where the route may change. Its limits are diameter and pressure, and it is never used on gas lines. Before fitting, cut the pipe end square and remove burrs.

An important point in compression fitting is that the pipe must go into the fitting to the marked depth and the nut be tightened with a strap wrench, not with a sharp tool that scratches the polypropylene. After fitting, the line is tested under pressure before backfill so any leak can be seen.

• PE compression fittings
• Compression coupling

In butt fusion the ends of two pipes, or a pipe and a butt-fusion fitting, are clamped in the machine's jaws, faced with the planer, melted on the heater and pressed together at controlled pressure so they become one piece on cooling. In our catalogue the butt-fusion 90° and 45° elbow runs from 63 to 630 mm, the tee and reducer from 110 to 315 mm and the end cap from 90 to 400 mm.

Our manual butt-fusion machine covers 20 to 63 and 32 to 125 mm, and the hydraulic machine 90 to 315 and 200 to 500 mm. The method is the most common permanent joint on main water and sewer lines and on larger diameters. Read the temperature, time and pressure of each weld from the pipe maker's table and the machine's instructions, and have a trained welder do the work.

The most important advantage of butt fusion is the low cost per joint, since it needs no intermediate fitting, only pipe and a machine. In return it needs enough room for the machine and a trained welder, and is difficult in a narrow trench or on a live line.

• PE butt-fusion fittings
• PE pipe welding machines

In electrofusion, the coupler or tee has a heating wire inside. The pipe ends are scraped, cleaned and pushed into the fitting, and the electrofusion unit reads voltage and time from the fitting's barcode and passes current through the wire. Because the pipes do not move and the weld data is recorded, the method is common on gas networks, repairs to live lines and tight spaces.

Our electrofusion coupler runs from 20 to 250 mm, with electrofusion elbows, tees and end caps in the same range, and the tapping tee for 25 to 250 mm main pipe. The electrofusion units work up to 160, 250 or 400 mm. In return, every joint is a separate fitting that has to be bought.

Each electrofusion fitting is made for one diameter and is not suited to pipe of a different diameter or beyond the permitted ovality. Coiled pipe must be re-rounded before jointing so it seats in the fitting; the alignment clamp is there for the same reason.

• Electrofusion fittings
• Electrofusion coupler

To connect to a valve, a pump or a metal pipe, a flange adaptor (stub end) is butt-fused to the pipe end and a metal backing ring behind it is bolted to the mating flange. Our stub end runs from 63 to 630 mm, and the backing ring, in galvanised or epoxy-coated steel and in ductile iron, is listed from 63 to 630 mm in PN 10 and PN 16 drilling.

To take a branch from a line, a compression clamp saddle is used on 32 to 315 mm main pipe with a 1/2 to 1 inch outlet, and on gas and drinking water the electrofusion tapping tee with its internal cutter does the same job by fusion.

If your valve or pump is threaded, a PE threaded adapter can be used instead of a flange; these adapters are also in the catalogue in the compression style. Ask what end connection the equipment has before ordering so you do not buy the wrong part.

• PE stub end (flange adaptor)
• Compression clamp saddle
• PE pipe clamp saddle

The table below puts the four methods side by side. The diameter range is from the published rows of our catalogue for the parts of that method, and other makers may have other ranges.

In short: compression for small diameters and irrigation; butt fusion for main lines and large diameters; electrofusion for gas, repairs and tight spaces; and a flange to reach metal equipment.

In the final choice, also consider access to skilled labour. If you have no qualified welder and machine on site, compression fitting or arranging a welding contractor may be simpler than buying a machine; we ourselves do not offer welding or rental services.

The quality of a fused joint depends on several things: clean, dry pipe and fitting surfaces, aligned and flat weld faces, even temperature, controlled pressure and time, and the joint staying still until cooling is finished. Welding with an iron or a flame controls none of these and is not advised for pressure lines.

Before service, the line is pressure tested as the project procedure requires, and on gas and city water lines the local gas or water company approves it. A joint that looks sound from outside may open under pressure; so have welding done only by a qualified welder with the right machine.

Cold, wind and rain also affect weld quality; in poor conditions weld under a shelter and keep the pipe surface clean and dry. Inspect each weld by eye before going on, and if you see a fault, cut the joint out and weld again.

• PE gas pipe: colour, standards and requirements

In your enquiry put the pipe outside diameter, the pressure class or SDR, the type of line, the jointing method you can use on site, the type of part (coupling, elbow, tee, reducer, end cap, stub end) and the quantity. For reducers and tees add both diameters, and for stub ends and rings the flange class PN 10 or PN 16.

We give technical advice on choosing the jointing method and parts before you buy and issue an official invoice. Send your list from the contact page and a pro-forma invoice will be prepared for you.

• Contact and quotation