Re-lined water main is well connected

The Viking Johnson Linergrip end termination system for thin-walled PE pipe has ensured the integrity of a newly rehabilitated 18-inch cast iron main carrying water for the Torbay area

The Viking Johnson Linergrip end termination system for thin-walled PE pipe has ensured the integrity of a newly rehabilitated cast iron main carrying water for the Torbay area.

The 18-inch main covers the final 9 kilometres from South West Water Tottiford water treatment works to Gallows Gate service reservoir, which supplies Newton Abbot, Teignmouth and Torquay.

Laid around a century ago, the main had developed significant leakage and suffered from pressure, discolouration and quality problems - familiar difficulties with cast iron that the water company recently targeted in the Newton Abbot area with a GBP9 million programme of rehabilitation.

Design and construct contractor Subterra - a division of Enterprise plc - has worked on a number of South West Water water mains, in some instances recommending complete replacement; but the section to Gallows Gate was considered sufficiently sound to permit the use of their own Subline close-fit polyethylene lining technique.

Subline uses thin-walled PE pipe folded on site, which provides sufficient clearance for it to be winched into the scraped and cleaned main between access pits.

The pipe is then reverted back to its circular form by pressurisation with cold water to break the temporary restraining bands, creating a close fit inside the main that seals against leakage and prevents future corrosion.

On the principle that a chain is only as strong as its weakest link, reliable end terminations between each section of the lined main are vital to ensure that the ends of both the PE and cast iron pipes are held firmly in place when the water supply is restored.

This was especially important on the section to Gallows Gate, which, although it is gravity-fed, reaches pressures of up to 25 bar in its descent towards the sea.

Add to that a PE pipe wall thickness of just 5.4mm, and the reasons for the Subterra decision to use Viking Johnson Linergrip are not difficult to understand.

The LinerGrip product was developed specifically as a termination method for mains relined with thin-walled PE liner pipe that is not self-supporting in an as-buried condition, and therefore relies on the host pipe for pressure retention.

As such, LinerGrip was able to accommodate the high pressures encountered at Gallows Gate.

Small diameter LinerGrip is available from stock in 4" and 6" sizes, with larger diameters manufactured to order.

The Subterra requirement in this case was for ninety-five 18"/DN450 LinerGrip products in both PN16 and PN25 configurations to make connections at all of the access points required by the lining operation.

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