Several ASTM Standard Specifications for installing both cured-in-place and fold-and-form liners contain notes to the effect that “this practice (lining) should not be construed to provide a 100 per cent watertight seal at all service connections. If total elimination of infiltration and inflow is desired, other means … may be necessary to seal service connections.”

Thus over the past few years a range of systems has developed to seal junctions in non-man-entry sewer pipelines. These are mostly variations on a hollow felt T-piece impregnated with resin, which is mounted on an inflatable packer and installed from inside the sewer main. Another variation provides a “top hat” where the “brim” of the hat seals around the rim of the cut junction, while the barrel seals up into the house service line.

So how long will these seals remain effective in a typical sewer application?

In Europe the application of such technology is now so widespread that in Germany, the City of Hamburg has developed a test to determine the resistance of such connections to repeated high pressure water jetting. This test formed the basis of a program undertaken by Interflow Pty Limited to confirm the effectiveness of the Lateral Connection Repair (LCR).

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Interflow’s LCR comprises a silicate resin impregnated felt t-piece. It is installed after lining of the sewer main from an existing manhole. CCTV monitoring confirms the correct location during installation, and the whole process is carried out remotely. Silicate resin is used rather than polyester as it has superior strength and adhesion with less shrinkage. It can be cured at ambient temperatures.

Testing was carried out at Interflow’s premises and was independently witnessed by certifying authority SGS.

The testing required assembling and lining of a section of 150 mm nominal diameter pipeline 20 metres long, containing 4 junctions – 2 in the soffit and 2 at the springline (12 o’clock and 3 o’clock.). Interflow LCRs were installed at these junctions. The junctions were pressure tested and an internal CCTV inspection conducted.

The test procedure comprised putting a specified amount of sand and gravel into one end of the pipeline section and water jetting it to the other end. The procedure was then repeated 30 times.

At the end of the testing the junctions were again pressure tested, the pipeline CCTV surveyed and the junctions then disassembled for closer inspection. Each junction passed the pressure test and the inspection of abrasion and wear on the liner and junctions showed that both could be expected to continue to perform satisfactorily into the future.

An important aim of the “Hamburg Test” is to simulate normal Water Authority practice in the use of jetting equipment and procedures. Thus if typically sewer mains are jetted every two years, than it could reasonable be said that the testing shows that the junction seals will last for at least 50 years.

With over 4,000 LCRs having been installed by Interflow over the past few years, there is now confidence that they will provide a long and effective life and that root intrusion and infiltration really will be a thing of the past.