Trenchless sewer pipe lining methods are innovative techniques used to repair or rehabilitate underground sewer pipes without the need for extensive excavation. These methods minimize disruption to landscapes and reduce the cost and time associated with traditional trench-based repairs.
Here’s a brief summary:
- Cured-in-Place Pipe (CIPP): CIPP is a popular trenchless method where a flexible liner coated with resin is inserted into the damaged pipe. The liner is inflated and cured in place using heat or UV light, creating a new, seamless pipe within the old one.
- Pipe Bursting: Pipe bursting involves breaking the old, damaged pipe while simultaneously pulling a new pipe into place. A bursting head fractures the old pipe as it moves through it, and the new pipe is dragged into position behind it.
- Sliplining: In sliplining, a smaller-diameter pipe is inserted into the existing damaged pipe. This method reduces the pipe’s interior diameter but provides a functional, corrosion-resistant liner.
- Pipe Coating: Pipe coating involves applying a protective layer, often epoxy, to the interior of the existing pipe. This method restores the pipe’s structural integrity and prevents leaks or corrosion.
Now that you have an understanding of what trenchless sewer line replacement entails, let us look at the 4 methods of sewer pipe relining as well as their pros and cons.
4 Methods of Trenchless Sewer Pipe Lining
When most homeowners hear about trenchless sewer line replacement, they tend to think that it is just one method. That is actually not accurate.
There are 4 methods of trenchless sewer line replacement each with its advantages and disadvantages. The cured-in-place pipe method is the most common of all and it is the one I will start with.
1. Cured-In-Place Pipe Lining
The cured-in-place pipe (CIPP) which is also known as epoxy lining or structural pipe line involves using a liner saturated with a 2-part epoxy resin to create a new pipe inside the old one.
Compressed air is used to shoot the epoxy-saturated/impregnated liner inside the old sewer pipe, which is then inflated and left to cure ambiently. The curing process can also be accelerated by the use of steam, hot air or UV light technology after which the liner is removed leaving behind a good-as-new pipe.
Here is how the process looks like:
Step 1: Sewer Line Inspection
The contractor uses a small sewer line camera to inspect the condition of the pipe. The camera is connected to a screen on the surface where the operator can see the exact location of the camera and the condition of the pipe.
Ideally, the operator will be looking for cracks, clogs, tree roots and corrosions inside the pipe to help them determine the extent of the damage and the amount of work needed to be done.
Step 2: Cleaning the Old Pipe
As you already know, the old pipe is always in a bad shape and the new liner cannot be installed in that condition. Corrosions, debris tree roots and other impurities will need to be removed.
The idea here is to try to as much as possible restore the pipe to its original size. That way, the new lining will be smooth which is important in the curing process and maintaining a uniform internal diameter.
A motorized chain is used to scrape the inside of the old pipe and water is used to flush out the debris. Hydro jetting is another alternative. The cleaning continues until the operator is satisfied that the pipe is ready to be relined.
Step 3: Measuring the Size of Existing Pipe
Most homeowners do not know the exact length of their existing sewer pipe. Measuring the size is important since it helps the operator to cut and prepare a liner that will be enough for the whole pipe.
The good thing is that the sewer inspection camera can help you with this. If not you will need to physically measure the exact length of the pipe.
Step 4: Preparation of the Replacement Liner
The replacement line is normally a felt tube made from fiberglass, polyester or other such materials.
One of the most first things that the contractor will do is to seal the pipe on both ends and suck out air from it. Air inside the pipe will create bubbles and prevent the formation of a consistent and smooth pipe inside the old one.
Step 5: Epoxy Preparation and Impregnation
The 2-part epoxy resin is mixed and stirred by hand in a bucket. This is usually a blue liquid although that doesn’t have to be always the case.
The felt tube is then saturated or as some people say “impregnated” with the epoxy ready to to be inserted inside the old pipe.
To insert the saturated tube inside the old pipe, you will need a piece of equipment known as an inverter drummer. Remember that the epoxy is inside the tube but you need it to be on the outside so that it can make contact with the old pipe and cure.
The inverted drum flips or inverts the felt tube inside-out but before that the tube is passed through rollers to make sure that less epoxy can be used for a long section of the tube and also since you don’t want to create a very thick pipe.
Step 6: Inserting the Tube in the Old Pipe
It is quite hard to push the already epoxy-saturated felt tube in the old pipe by hand. That is why an air compressor is needed.
The air compressor uses compressed air to shoot the tube into the old pipe. Once inside the compromised pipe, you will need to inflate the tube so that it sticks to the wall and cures there.
Another liner is inserted inside the tube and pressurized inside the felt tube so that it fully inflates it to leave a smooth pipe inside.
Step 7: Curing of the Liner
Curing basically means solidifying. The tube is left to cure ambiently, which takes time or it can be accelerated through other methods.
Curing using steam or hot air will take anywhere between 4 and 12 hours while modern LED blue light curing will take 1 to 2 hours.
After curing, the lining is deflated and removed leaving behind a good-as-new sewer pipe which will last for the next 50 to 70 years.
Step 8: Inspecting the New Pipe
The contractor will afterwards inspect the new pipe just to be sure that everything has gone according to plan. Please note that some contactors will skip this process altogether.
With the new pipe cured and inspected, services can then resume,. Your drains will be reconnected to the sewer line and you can then continue enjoying your new pipe.
2. Pipe Bursting
Pipe bursting, as it name implies is a trenchless sewer line replacement method where the old sewer line is expanded and broken then new high-density-polyethylene (HDPE) pipes are pushed through it.
In pipe bursting, there is an entry and exit Pit. These are 2 pits dug on both sides of the pipe (from where the relining starts to where it ends).
I know I said that trenchless sewer line replacement does not require ground excavation but in this process you will need it although not to the same degree you would if you were replacing the entire pipe.
So, how is the old pipe expanded and broken and how are the HDPE pipes installed? Quite easy!
A pulling head, which is also known as a bursting head or a bullet is pulled through the old pipe with the help of a hydraulic power pack.
The pulling head breaks/fractures the old pipes while at the same time pulling and laying the HDPE pipes inside it.
The main advantage of the pipe bursting method over other trenchless sewer pipe replacement method is that you can replaced the old pipe with another one of the same size or even larger diameter.
It is especially a great choice if you are replacing your private lateral sewer line.
3. Spray Lining
This method is very similar to the cured-in-place pipe replacement method but it is not as popular. Some people even use the 2 methods interchangeably to refer to the same thing although they are totally different.
The main difference between cured-in-place and spray lining sewer pipe replacement methods is that the spray lining method does not use a felt or fiberglass liner, which is used in CIPP. It is therefore NOT structural.
In spray lining, the interior of the old pipe is coated with an epoxy or flexible polymer. These are usually sprayed on or brushed on, and that is why this method is also known as brush coating.
The end result is very similar to that of the CIPP. For vertical pipes like those used in apartment buildings, flexible resins are preferred to resins since they resist cracking when the building moves.
The main advantage of spray painting/brush coating over cured-in-place sewer line replacement method is that the former can be used on pipes of up to 1.5 inches in diameter while the latter doesn’t do well with pipes of 2 inches or less.
4. Slip Lining
This particular trenchless sewer line replacement method works well with old and large pipes. Most homeowners will definitely not need it.
Slip line pipe relining involves pulling a pipe of a smaller diameter (usually HDPE) through the old pipe and then filling the space between them using grout.
Needless to say, this method reduces the flow capacity of the sewer pipe which is one of its main limitations and will therefore not work with pipes of smaller diameters due to code requirements.
Pros and Cons of Trenchless Sewer Pipe Replacement
The following are the advantages of and disadvantages of trenchless sewer pipe replacement, starting with the advantages.
1. Reduces Cost
Plumbing is so expensive in the United States (and probably everywhere else). Any method which can be used to reduce the cost of a project without compromising the quality is therefore very welcome.
Trenchless pipe lining can reduce the cost of replacing a pipe by about 30 to 40 percent. That is huge. If for instance you were to pay $5000 using the traditional method, you would only end up spending $3000 to $3500 using trenchless methods.
In most areas, trenchless sewer relining is usually a 2-person job. Now compare that with the traditional way of doing it.
With all the digging and patching up needed later (not to mention the heavy lifting), you will need a big crew to do the job. More people and equipment means the cost will definitely go higher
2. Saves Time
Trenchless sewer line replacement methods takes about 2 to 3 days to complete, including the curing process. That is remarkable.
On the other hand, traditional sewer line replacement method can take weeks. That is pretty inconvenient considering that you cannot stay in a house without a sewer line.
What is the distance between your house and the street or septic tank? That is also the length of your lateral sewer line.
If that is the pipe you need to replace, try to imagine a long and deep trench cutting across your front yard for days! And even when the process is complete, you will steel need to go back and plant grass, repair sidewalks or event plant new trees.
With trenchless sewer replacement, you will not have to deal with any of that.
4. Lasts Long
Relined pipes which are in essence made from plastic can last for a very long time. Unlike cast-iron pipes, plastic is corrosion-resistant and is also not penetrated by tree roots.
The main disadvantage of cast-iron sewer line pipes is that they corrode over time and weaken which makes them leak. Their interior also becomes rough and the internal diameter reduces which results in clogs and sewage backups.
So are there disadvantages to the trenchless sewer pipe replacement methods? Yes there are and here are some of them:
1. Not Ideal for All Pipes
As you already know, sewer lines are not all made from cast-iron. Some are many from Orangeburg or even clay.
Unfortunately, a process like cured-in-place pipe cannot work on Orangeburg and other fragile pipes. The pipes may collapse during the cleaning method (hydro jetting) even before they are relined.
2. Old Pipe Restrictions
One thing to notice is that a method like pipe bursting can only be used for horizontal sections of pipe. If a pipe has many bends or curves this method will not be ideal or it can turn out to be very expensive.
With pipe bursting, the sections of pipe being replaced also need to be longer than 15 feet. This is because you will need an entry pit and exit pit which both measure 4 feet by 4 feet hence you will a good distance between them.
Also, methods like CIPP, spray or slip lining will reduce the internal diameter of the pipe which also means reduced volume of flow.
So which is the best trenchless sewer pipe relining/replacement method? You will probably need to consult a plumber for that.
Pipe bursting is however time-tested and the most preferred method when replacing your private lateral sewer line. The pipe also lasts longest (50 to 100 years).