Underwater pipe relining an Australian first (case study)

Nuflow Rockhampton

Relining cracked and leaking sewer pipes was nothing new for Nuflow Central Queensland’s Ben Byrne. But doing the reline on a live line being pumped under pressure to the treatment station made it a great test for the company’s latest star product – and made underwater pipe relining an Australian first!

The client

Rockhampton Council Sewer Network.

The problem

A cracked and leaking 100mm junction connecting to a 150mm main sewer line. Pipe material: earthenware (terracotta).

The junction serviced a busy shopping centre amenities and closure of the line or the main which led to the council’s treatment facilities, was not an option.

Solution – underwater pipe relining

By using Nuflow’s underwater and fast-curing Blueline resin the junction was successfully relined using the pull-in-place method of installation whilst the line remained live and fully functional.

Time taken to resolve the issue

Six hours

Disruption to services, lifestyle, functionality


Cost saving over digging

Between $5,000 and $10,000

Other benefits

  • No heavy machinery required
  • No traffic diversions or traffic control
  • No line closures and associated inconvenience to shopping centre patrons
  • No environmental impact
  • No WHS issues
  • No disruption to local residents

Underwater pipe relining an Australian first

Another day at the office

Ben Byrne, Nuflow Central Queensland

As far as Nuflow Central Queensland’s Ben Byrne was concerned it was pretty much just another day at the office. He’d been called in to reline a cracked junction in a failing sewer system which serviced Rockhampton’s Stockland Shopping Centre. With so much of regional Australia’s underground waste and water infrastructure approaching end of life, this was what Byrne usually refers to as a ‘bread and butter’ job but there was certainly something different about the way the bread was being buttered for this particular junction.

Thirty years ago there would have been little choice but to excavate the area, remove the damaged pipes and lay new ones. Even as recently as last year, the popular trenchless (no dig), epoxy resin (CIPP) relining alternatives used widely throughout Australasia today would have required a dry line. That would have meant shutting down the sewer and either closing the amenities block in the busy commercial complex or having trucks pump and transport sewage by road. All of these repair strategies would have been costly, time-consuming and inconvenient, which was why Byrne was so excited about putting a new alternative to his client.

That alternative was a new advanced composite resin and liner designed to cure under water.

This job was Byrne’s first big test of the product and he knew that if it worked, relining underground pipes and junctions was about to get a whole lot simpler.

Cracked and leaking sewer pipes

The job itself was pretty standard; a cracked and leaking junction in aging underground sewer pipe infrastructure.

Area above the cracked sewerage pipes

The pipes were made from earthenware (terracotta/clay) and were approximately 60 years old. Ground movement over time meant cracks were leaking sewage into surrounding soil and allowing vegetation to enter and impede the flow of the pipes.

Although the line serviced the major shopping centre, it was outside the perimeter (meaning it was council’s responsibility), and with a job requirement that the line remain operational during repairs, Byrne knew things weren’t going to be easy.

“Our standard Blueline system just wasn’t going to cut it,” Byrne said, “because it was a pumped sewer line under continual flow from the shopping centre.

“The main line was 150mm wide and the junction that came into it from the shops was 100mm, with the whole thing buried about six metres deep, beneath roads and driveways.

“Digging it up and excavating was totally out of the question.

“The waste goes to a holding station and is then pumped down this line to the council’s waste treatment facilities, so the pipe’s basically three quarters full the whole time and running under force from the pump.”

The pipe relining solution

Byrne knew that Nuflow’s Research and Development team had been working on a new resin, capable of being cured under water, and made some enquiries.

“I already knew we were the only ones who could reline these sorts of junctions cost-effectively but given that it was all under water and that we’d have to work against the flow of the pump it wasn’t going to be easy,” he said.

Once he confirmed with head office that the new product could handle the job specs, he set about formulating an installation strategy.

“There were lots of smaller lines feeding into the main from houses or other shops in the street, and this particular line came up vertically 6metres to the surface.

“We used an existing manhole opening to get our rope from the ground down this 6m line and then floated it all the way along to another manhole downstream where we caught it and pulled it out.

“From there we tied our reline and internal bladder on and (with the pipe under continuous flow) dragged it all the way back up the line about 60 metres to the damaged junction.

“Once we had it in place we simply inflated the bladder to initiate the curing process, and then waited until we knew it was rock hard and completely bonded to the interior pipe walls.

“After that we just pulled out the bladder and the reline stayed put.”

Because the junction reline was relatively small, Byrne didn’t need a lot of preparation time and so used the fast-curing formulation of the underwater resin.

“Nuflow has done a lot of testing with resin cure times and they give you all the calculations for the different resins,” he said.

“We kept an eye on everything and had a test sample of our own from leftover resin, so we knew exactly when to remove the bladder.

“No one even knew we had a line in place and once we pulled it out no-one would have known we’d been there basically. We started about 8.30 on the Friday morning and we were done by 2.00pm.

“Not only did we manage to reline the pipe successfully while fully submerged, we actually pulled the liner into place against really high resistance, because of the work the pump was doing sending the waste in the opposite direction, so I was definitely happy with how the whole thing went.”

Few other relining options available

Byrne said other relining companies, or even the Nuflow composite resin liners he’d used previously, simply wouldn’t have been able to do the job.

“For the big relining companies who do long lengths at a time, it just wouldn’t have been worth it because they would have had to shut down the whole line, reline the main and then use a robotic cutter to make the holes for the junctions, which is a very expensive exercise,” he said.

“They’d also have had to stop the sewer flow which is no small feat in a pumped line from a major shopping centre.

“Once they blocked it they’d have had to keep pumping sewer out into trucks as the chamber filled, then transporting it to the council waste facility on a rotational basis.

“Those trucks are about $200 an hour, so that’s even more expense.”

Repairs was carried out via this open manhole eliminating the need for digging or disruption

According to Byrne, even if the bulk of the work had been carried out after hours, it would still have been a major operation and traffic control around the access sites to the pumping chamber would have been needed.

He says the relining systems he’d previously used wouldn’t have met the challenges of this job.

“You couldn’t have done it with our standard relining materials either because the water would have washed the chemicals out as we were dragging the liner through.

“The liners are made from a soft, felt material and you mix your two-part chemicals together and impregnate the felt with it.

“While it’s still wet and malleable you can roll it up and drag it into place, but if the liner comes into contact with water while it’s wet the resins don’t cure properly because some parts get washed away and you’re left with furry sections.

“Those things don’t happen with this new resin because it’s not affected by water.”

How underwater relining was developed

Nuflow operates as a complete end-to-end relining solution, where the product development, manufacture and installation are all a part of the one coordinated effort. Installations are done by licensed franchise partners who complete a two-week, TAFE-accredited training course when they commence, and attend ongoing training sessions each year to stay up to date with developments.

According to Byrne, Nuflow’s scientific team developed the new resin out of necessity because a common theme that arose at the education and training sessions was the troubles installers were having with unanticipated water affecting the cure of the resins.

What the team wanted, was a resin that could cure under water.

Dr. David Rogers, head of Nuflow’s Research and Development team attended some of those sessions and listened to installers’ concerns.

“Quite a few of our installers were saying water infiltration was causing them issues,” he said.

“They told us even though CCTV footage showed the pipes themselves were clear, by the time they actually did job, water from the subsoil above or around the pipe had often filtered in through cracks and was now sitting in the pipes.”

Initial underwater curing trials were conducted at Nuflow’s R&D facility, using standard fast, normal and slow resins. These trials clearly demonstrated the problem: when water was present, resin washed off the felt liner, and in most cases created an oily film on the surface of the water. Even after a day or more, some of the resins remained sticky and under-cured.

An extensive search was conducted, aimed at identifying alternative, innovative hardeners that could repel water before and during the curing process.

“What they really needed was a resin that would be able to cure completely in the presence of water,” Rogers said.

A program of R&D was conducted over several months. Some of the new candidate hardeners cured underwater but were problematic in other ways such as expense, incompatibility with Nuflow resins or low mechanical problems when cured. However, one by one, these drawbacks were overcome and by March 2019, two new underwater curing resins (including a fast-curing version) had been developed.

Each had similar viscosity, working and cure times, and strength to Nuflow’s standard normal and fast resins.

“We did an underwater curing resin demonstration at Nuflow’s annual training in April,” Rogers said.

“We got a couple of the guys to do a small patch repair on a PVC pipe which was totally submerged in water during cure.

“After about one hour, the pipe was removed and the reline patch was cured completely hard, with no stickiness.

“That was when we all knew we had something that really worked.”

Often the setting up, labour and installation costs are as high or higher than the cost of relining materials themselves, so having a product that could save time and the possibility of a failed reline due to water exposure could mean significant cost savings overall.

The successful formulation was developed a little over 12 months ago, but the products had to undergo rigorous trials and testing before being released.

Rogers said Byrne’s willingness to trial the new product helped it launch into the market.

“One of the advantages of Nuflow being a local company with its own research labs and manufacturing facilities in Australia, rather than in Europe, is that we can be highly responsive to what our installers and the New Zealand and Australasian markets need,” he said.

“If we see there is a need for something or a problem others can’t fix, we have the leading scientific and engineering capacity on hand right here to come up with solutions.

“But while we can do all the testing and checking in the labs, until people start actually using the products out in the field it’s all just talk, really.

“Byrne was really positive about trying this new product because he could see its potential, and now he’s reaping the rewards.”

Advantages of underwater relining with Nuflow

By using Nuflow’s underwater-curing resin on this job, Byrne believes the client saved between five and ten thousand dollars, as well as the disruptions and potential workplace health and safety and traffic hazards that other alternatives would have presented.

“Apart from the cost savings there was no need to block the sewer, or bring in heavy machinery or trucks to keep the sewer chamber running,” he said.

“We also have a very small footprint, so it’s better for the surrounding environment as well.

“Basically we’ve just gone in there, got the job done, and no-one even knew we were there.”

Looking to the future with underwater relining

Byrne believes the underwater resin, which will soon be used to reline AC tidal storm water pipes in northern New South Wales, will ensure Nuflow’s CIPP relining systems become even more popular.

“Most pipes have water in them when you’re doing sewer and storm water so having a resin that’s not affected will make a huge difference,” he said.

“We’ve trialed the resin on a couple of other relining jobs this year where pipes have had bellies in them and were holding water and we’ve had to pull lines over long distances and they’ve worked fine.

“Also, if you’ve got to do something in a line that’s got 30 houses connecting into it, it’s pretty hard to run around telling everyone they can’t use their water or toilets for an hour while you work, but with this new underwater resin there’s no drama.

“It’s the only stuff we buy now.

“It’s making a massive difference and I think it will eventually supersede the other resins.”

If you have any questions about underwater pipe relining or you’d like a quote, visit our contact us page.

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