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Trenchless Sewer Repair – The Future Is Here

 

Trenchless sewer repair is a no-dig way of repairing or replacing old and leaking underground pipes. Rather than digging a trench to fix the old pipe, this method only requires digging small holes to access the pipes if they are buried. No digging is required if the sewer line is accessible  through manholes or other convenient access points.

These days, an open-cut sewer replacement is the least effective option because of the risk of damaging the extensive network of street utilities and the potentially severe negative traffic impacts.
 

Trenchless Sewer RepairTrenchless Sewer Repair


Trenchless sewer repair is commonplace in the repair of sewer lines. Many cities are using this technology because of the significant advantages of reduced time to repair and reduced disruptions. Many repairs can be completed within 1 day.


This procedure can be used for:

  • Manhole repairs
  • Sewer line spot repairs
  • Sewer lining rehabilitation
  • Water main lining rehabilitation

 

Before Starting any Trenchless Sewer Repair

The problem can usually be identified by using a sewer inspection camera.

Trenchless Sewer Repair - Sewer Inspection CameraSewer inspection camera being lowered into sewer

Some cities use a CCTV video sewer inspection camera system to monitor the condition of their sewer system. The system helps to determine their maintenance and rehabilitation needs.

 

Trenchless Sewer Repair Technologies

Lines can be repaired or replaced without damaging the surrounding infrastructure. A number of methods are available for this type of repair:

Cured-in-Place Pipe (CIPP)

One of the most widely used trenchless sewer repair methods and can be used on pipes from 3” up to 110”. 

CIPP Installation Method

A non-woven polyester tube made of felt is impregnated with a thermosetting resin (like Styrene) with catalyst. This lining tube is blown in from 1 point or pulled between 2 access points (manholes or access holes) using air or water pressure and then inverted.


CIPP Repair ProcessCIPP Repair Process

Then steam, hot water, or UV light  is used to cure the resin mix  to form a tight fit against the existing sewer walls. These repairs can be performed quickly and the whole procedure can take less than a day. However, this method cannot be used if the pipe has collapsed somewhere.


Pipe Bursting

Pipe Bursting Method

A new pipe is pulled through the old pipe using hydraulic machinery, completely replacing the old/broken pipe. Can be used on pipes from 2” to 36” (has been used up to 48”) . HDPE and MDPE are the most common replacement pipes used in this method. Cast iron, vitrified clay, and reinforced concrete pipes can also be used.

This method requires 2 access points.
 

Trenchless Sewer Repair - Pipe Bursting Revealed

A bursting head is attached to the replacement pipe and is pulled through the old line.  The bursting head breaks up the old pipe as it gets pulled through. The head is attached to a pulling cable that is drawn using a winch powered by hydraulics.

This method can be used to replace pipes with same size diameter or larger.


Slip Lining

Slip lining pipe can be either continuous or segmented.  Lengths can be tied together using a thermal fusing machine.

Trenchless Sewer Repair - Slip Lining

Generally less expensive than CIPP, a high density polyethylene (HDPE) pipe is slipped into the older piper, the space between the pipes is grouted, and then the ends are sealed. Laterals are connected with saddles and banding.


Trenchless Sewer Repair - Slip LiningBefore and after slip lining


Requires two access points via a small excavated entry trench to provide access to the host pipe, or to a manhole if the insertion will begin there.  Also, a lubricant such as bentonite can be used to facilitate the slipping action required to insert the pipe.

It is also recommended to push and not pull the pipe through. Pulling can elongate or stretch the new pipe out of shape.

This repair always results in a smaller diameter pipe.


Grouted-in-Place Pipe (GIPP)

Trenchless Sewer Repair - Grouted-in-Place PipeGrouted-in-Place Pipe

A patented trenchless sewer repair method by Groling in Germany called The Trolining System. This method can be used on larger pipes ranging in diameter from 2-2/3’ to 6-1/2’. It is based on high-density polyethylene (HDPE) liner components,and uses V-shaped embedment studs. The space created by the studs is filled with a specially engineered injection grout that fixes the liner permanently in place and provides the load-bearing shell of the system.
 

 

Shotcrete/Gunite Lining

Trenchless Sewer Repair - Shotcrete

“Dry mix” or “wet mix” concrete is “sprayed” onto the existing sewer once a reinforcement structure is built in place. Gunite is simply a trademark for the dry-mix shotcrete process.

 

Thermoformed Pipe

Trenchless Sewer Repair - Thermoformed Pipe Insertion

A polyethylene (Deformed & Reformed) or PVC alloy ( Fold & Form) pipe, smaller than the original broken pipe is pulled through the existing pipeline using a winch. Pipe sizes of 3” to 30” can be repaired. Continuous lengths of 1500 feet in the smaller diameters and 800 feet in the larger diameters can be used.



Trenchless Sewer Repair - Thermoformed Pipe Curing

Once inserted, the pipe is heated using steam and air pressure, to let the material "relax", which resets the material's "memory" to the new size and shape of the pipe it is in.



Trenchless Sewer Repair - Thermoformed Pipe Installed

Thermoformed pipes usually leave a pronounced dimple at each lateral connection. Robotic equipment is used to reinstate these connections.


Once installed, the thermoformed pipe will not return to its original size or shape after it has cooled, nor will it shrink in length. It will take on the shape and size of the original sewer pipe.


Spot Repair

Trenchless Sewer Repair - Spot RepairSewer Sealer™ Sleeve from Link-Pipe

Special sleeves or short sections of CIPP are installed inside the pipe only in the area where the pipe needs to be rehabilitated. With the help of a sewer inspection camera for proper placement, the sleeve is sealed in pace with grout or glue.

This provides a more economical way to maintain sewer lines. Instead of replacing the whole pipe section, only the damaged section is repaired. Properly done, this can provide a huge cost saving.

 

 

Which Trenchless Sewer Repair Method Do I Choose?

For most residential repair jobs, CIPP or Pipe Bursting would be used. These methods generally cost more than conventional digging, but will minimize the destruction of the homeowner’s property.

Municipal repairs are a lot more complicated and will require an evaluation by the city for each particular condition, considering the location of the pipe and the nature of the break.

From one city’s experience, CIPP is used when:

  • Sewer is deep underground;
  • There are abrupt changes in direction and/or grade;
  • Host sewer pipe is 8 inches or smaller;
  • Existing sewer laterals need to be retained – a robotic cutter makes holes in liner to connect to existing laterals. Comparatively, slip lining needs an excavation at each lateral connection.


For more information on trenchless sewer repair technologies please contact sewer contractors in your area. Please take note that technology is evolving at a rapid rate and new techniques and materials are being introduced by trenchless sewer repair manufacturers.

 

Related article: A Trenching and Excavation Revolution Is Underfoot

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