Underground pipe repair methods

By Francesco Lo Presti

The underground plumbing system is crucial in ensuring the smooth flow of water and waste disposal. However, these underground pipes are, “Susceptible to damage due to various factors, which can lead to costly repairs and disruptions in daily life,” said Alex Meyer, product manager at Ridgid.

It is common practice for municipalities to have legislation in place that ensures the underground piping system is in good shape and has been inspected, “Anytime a house changes hands or a mortgage changes hands, municipalities require that somebody comes to inspect the main thread that goes from the building onto the street,” explains Dave Dunbar, national sales manager at General Pipe Cleaners. This means that when a property’s plumbing line hasn’t been properly inspected, the owner could be in for a potentially challenging and costly situation.

Reading the signs
Repairing and maintaining underground pipes is an essential skill for plumbers to possess. According to Dunbar, this means that they need to “have a thorough understanding of underground pipe repairs so they can effectively diagnose and address situations.”

The first sign that an underground pipe has been damaged is looking for slow or blocked drains, unpleasant odours, or water stains. “Also, if you look out and see a sinkhole or any sunken areas, you know there’s an issue,” said Meyer.

Improper installation can create stress on the piping system, which can result in cracks or sinking of the line, explains Sean Comerford, technical applications manager at Oatey. Additional indicators for a damaged pipe include slower running times for sinks or toilets. Meyer states, “People need to be conscious of what they are flushing down the pipe.” Not all flushable wipes are safe to go down the toilet.

Keeping an eye on the signs of damaged pipes is critical. But another important step is understanding the surrounding area and some of the common causes of pipe damage. “Any homeowner or contractor should constantly be aware of what’s happening around the property. Common causes of underground pipe damage include tree root infiltration, aging infrastructure, and corrosion,” explains Dunbar.

Once the situation has been assessed, it’s not just as simple as seeing and treating the problem. “Until a plumber can open a blockage and inspect the pipe with a camera, you’ll never know the full extent of the damage. But once you do your camera inspection, that’s when you’ll see any cracks, displacements, or total voids in the pipe,” said Dunbar.

Underground pipe material
Some types of pipes are most susceptible to cracks and damage. This is largely due to its durability. “One pipe that we know was susceptible to cracks or damage was an Orangeburg pipe. A lot of this pipe was laid in the United States in the 70s and it was a cheaper material at the time. People quickly found that a lot of these Orangeburg pipes were failing after 10 to 20 years. Unfortunately, there’s still a lot of that in the infrastructure that’s getting dug out and replaced,” explains Meyers.

Even the best system can result in issues. It just depends on the use of the system. “It depends on what people are flushing and also how often. There is also just a natural wear and tear of a system, and most pipe materials, when installed, were designed with about a 50-year life expectancy,” said Dunbar.

Each different type of pipe requires its own repair techniques. For instance, repairing plastic pipes is typically an easier task with fewer risks. “Clay or cast-iron pipes, on the other hand, can be more challenging as they may crack or crumble during the cutting process. Extra care is needed to avoid further damage,” explains Comerford. The most common underground pipes typically include cast iron, PVC, ABS, and clay. Dunbar adds, “Cast iron pipe is one of the major types of materials still in the ground. There is a lot of it in use, especially in big cities.”

Repairing underground pipes
As previously mentioned, the most common underground pipe repair method involves excavation. “However, this comes at a higher cost and it’s also an inconvenience to the homeowner,” said Meyer.

While this is the most common method, over the years, the industry has introduced new technologies to help make pipe repairs less invasive. “We’re seeing that a lot of pipes can now be repaired from the inside out—trenchless repair methods, like pipe lining or pipe bursting. The pipe bursting method involves putting a new pipe into the damaged one, and then forcing the old one apart. Both these methods can help minimize disruption to the property while repairing damaged underground pipes,” explains Dunbar.

Another standard method is cured-in-place pipe, or CIPP, “which is a method that involves inserting a new pipe liner coated with epoxy resin into the damaged pipe, inflating it, and letting it cure in place,” explains Dunbar. When working with the CIPP method, there are two additional specific types of CIPP, pipe patching and pipe relining.

Pipe patching is a method that can be done for short repairs (six feet or less). The process involves taking an inflatable packer and putting a fibreglass liner over it. “You mix resins and saturate that liner, then push that whole packer and system into the ground and the pipe, and when it’s at the point where you have that pipe repaired, you inflate that packer. As those resins are curing on that liner, it’s doing a chemical reaction that’s now creating a new material that will solidify that repair. Then, after about an hour and a half of carry, you deflate that packer, you pull that out, but that fibreglass liner pipe patch stays in there,” explains Meyer.

When it comes to pipe lining, “This method is usually done for repairs of up to 100 ft. or so, and it coats an old pipe with a lining, which then hardens. With this, you’d start using a liner or a flexible tube and blow into the pipe. You’d then infuse it with epoxy and put the front end inside the pipe that is going to be relied on. You turn it on from there, creating positive pressure that blows the epoxy down the pipe. Then you cut out the back end, and you let it cure. Once that process is done, you must go through and reinstate the pipe,” explains Dunbar.

During a pipe repair or replacement, solvent welding is a plumber’s best friend. This process requires specific considerations, especially when working with large-diameter pipes. “There are five tips to remember while solvent-welding large-diameter PVC, ABS, or CPVC plumbing systems. Using the proper tools and practices, using the right primer and cement, using the proper tool for cement application, using more than one person or a specialized tool to help the connection, and prefabricating as much as possible,” explains Oatey in its resource guide titled “Five Tips for Large Diameter Solvent Welding.”

Staying in the game
Underground pipe repairs can offer plumbers callback opportunities. “People call all the time because their drain is clogged, but not every one of those calls will result in a relining job or any replacement job. Maybe one or two out of 10 will result in those jobs,” said Dunbar. It’s best practice to always equip work vehicles with the necessary tools for the job. “There are tons of service trucks on the road with snakes, jetters, cameras, flexible shaft devices, etc. This allows a contractor to prospect for those pipe replacement jobs. You go in for a simple clog in the drain, but by having this extra equipment, you can analyze a pipe’s situation and see if there’s any extra damage,” said Dunbar.