Before a sewer line is lined, it must be cleaned to a near-bare wall: roots cut flush, grease and sediment flushed out, and scale or tuberculation removed from cast iron. Hydro jetting, often combined with mechanical cutters and descaling tools, does this work. Poor prep can leave wrinkles, lumps, poor adhesion or blocked connections in the liner, which are hard to fix once the resin cures.
- Liners follow the shape of whatever is under them, so debris left in the pipe becomes a permanent lump or wrinkle.
- Prep typically combines jetting, root cutting and, for cast iron, descaling with chain or abrasive tools.
- A camera verifies the pipe is clean and measures lengths, diameters and connections before the liner is made up.
- Prep cleaning can reveal that a section is too damaged to line and needs excavation instead.
- Ask how prep is done and whether you will see the before-lining video; it is part of the quality of the job.
01 /Why does a pipe need jetting before it is lined?
A pipe needs jetting before lining because a cured-in-place liner takes the shape of the surface it cures against. Cured-in-place pipe (CIPP) lining inserts a resin-saturated flexible tube into the old pipe, inflates it against the wall, and cures the resin into a new pipe inside the old one. Anything left on the wall, such as roots, grease, scale or a pile of sediment, is trapped under the liner. The result can be a lump that catches debris, a wrinkle, a reduced diameter, or an area where the liner does not bond or seat properly.
Other trenchless methods have similar needs. Pipe bursting pulls a new pipe through the old one, so the old pipe must be passable. Sectional point repairs need a clean spot to seat the patch. In every case, cleaning is not optional prep; it is part of the repair.
02 /What does lining prep cleaning involve?
- Initial camera assessment
The line is inspected to confirm material, diameter changes, connections, defects and whether lining is suitable at all.
- Opening and bulk cleaning
Jetting flushes grease, sludge and sediment. A penetrator opens any stopped sections first.
- Root removal
Roots are cut flush with the wall using root-cutting nozzles or mechanical cutters. Protruding root stubs can puncture or deform a liner.
- Descaling (cast iron)
Tuberculation and scale are removed with chain knockers, abrasive or carbide cutters driven by a drill-type machine or water, returning the pipe toward its original diameter.
- Flushing
A final flushing pass removes all loosened fragments from the pipe.
- Verification camera
The pipe is inspected end to end to confirm a clean wall, and lengths and connection positions are measured for the liner.
Nozzle types used in these steps are described in jetting nozzles explained.
03 /How clean is clean enough for a liner?
Timing matters as well. Prep cleaning is usually done shortly before the liner goes in, often the same day or the day before, because a cleaned line starts collecting grease and debris again as soon as the household uses it. Installers commonly ask for water use to be limited during the lining window, and they may bypass or plug upstream flow so the resin can cure without water running over it.
Clean enough generally means the pipe wall is visible along the full length, with no protruding roots, no loose debris, no standing sediment, and scale reduced to the point that the liner can seat smoothly. Liner manufacturers and installers set their own acceptance criteria, and some municipal and commercial specifications set formal cleaning requirements. For a homeowner, the practical test is the verification video: if you cannot see the wall clearly, neither could the installer.
| Left behind | Possible liner result |
|---|---|
| Root stubs at joints | Bumps, punctures or points where debris snags |
| Grease film | Poor contact or bond with the host pipe |
| Sediment in the invert | A ridge or reduced bottom diameter |
| Heavy tuberculation in cast iron | Lumpy liner, reduced diameter, areas that do not seat |
| Water flowing from upstream | Resin washout or poor cure if flow is not bypassed or stopped |
04 /Is descaling cast iron risky?
Descaling cast iron carries a real risk of breaking through thin areas, and that risk is part of why the pipe is being lined. Decades of corrosion can leave a cast iron invert paper-thin under the scale. Removing the scale can expose or open holes. For lining, that is often acceptable, because the liner becomes the new pipe and bridges small holes, but only within limits set by the liner system. Large missing sections, collapses and severe offsets may need an excavated repair before or instead of lining.
Material-specific cautions are in is hydro jetting safe for old pipes.
05 /What can prep cleaning reveal?
Prep cleaning often reveals the true condition of the pipe for the first time. Roots and grease hide cracks; scale hides thin walls. When the wall is finally bare, the installer may find:
- Sections too collapsed or offset for a liner to pass or seat properly.
- Sags that a liner would follow, leaving a belly in the new pipe.
- Connections, such as a branch line, that need to be reinstated after lining.
- Diameter changes (for example, 4-inch to 6-inch) that the liner must be designed for.
- Material transitions, such as cast iron to clay at the foundation, that affect the plan.
Each finding has a practical consequence. A section that cannot be lined is typically excavated and replaced as a point repair, after which the rest of the run can be lined. A belly that the liner would follow means the new pipe will still hold water at that spot, so some owners choose to dig and correct the grade there first; bellies are especially common in plastic laterals whose bedding settled, as explained in is hydro jetting safe for PVC and ABS. Branch connections that the liner covers are reopened afterwards with a remote cutter, and the camera confirms each one is fully open. Diameter changes and material transitions affect liner sizing and resin quantity, which is why installers measure them during prep rather than guessing from the outside.
A good quote anticipates these possibilities and explains how they will be handled and priced. It is reasonable to ask how the price changes if the prep camera finds a section that cannot be lined.
06 /Does lining stop roots and grease for good?
Lining seals joints and cracks, so roots generally cannot re-enter a properly lined section. That is often the reason chronic root problems are lined. Grease is different: a liner provides a smooth wall that may build up grease more slowly, but grease still comes from the kitchen, so prevention still matters. Lined pipe can be jetted for maintenance; ask the installer which nozzles and pressures the liner system allows, and pass that information to any future contractor.
Root problems and the jetting-versus-lining decision are covered in jetting roots in sewer lines, and our sister site SewerRoots.ca goes deeper on long-term root solutions.
07 /What should a lining quote say about prep?
- What cleaning methods will be used (jetting, root cutting, descaling).
- Whether prep is included in the price or billed separately.
- Whether you will receive the pre-lining and post-lining camera video.
- What happens if prep reveals a section that cannot be lined.
- How branch connections will be reinstated and verified.
- What jetting the liner allows for future maintenance.
Compare prep approaches across contractors with the quote request form, and see typical cleaning ranges on the hydro jetting cost page.
FAQQuestions people ask
Do pipes need to be cleaned before CIPP lining?
Yes. Liners conform to the surface they cure against, so roots, grease, sediment and scale must be removed first, and the result verified by camera.
Can a collapsed pipe be lined?
Usually not where it is collapsed. A liner needs a continuous host pipe to pass through and seat against; collapsed sections are typically excavated first.
Why is descaling done before lining cast iron?
Tuberculation reduces diameter and creates an uneven surface. Descaling restores the bore so the liner seats smoothly and keeps as much diameter as possible.
Can a lined pipe be hydro jetted?
Generally yes, within the liner system's guidance on nozzles and pressure. Ask the installer and keep that information for future contractors.
Does prep cleaning cost extra?
It depends on the contractor. Some include it; others quote it separately. Ask for it to be stated clearly in the quote.
How long does lining prep take?
For a typical residential lateral, prep often takes a few hours, longer for heavy roots or cast iron descaling.
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