Homeowners researching a failing stack quickly meet two camps: contractors who replace pipe and contractors who line it, each presenting their method as the obvious answer. Cast Iron Oshawa sits with neither camp — partner plumbers quote what the camera footage supports, and on this page the two methods get compared the way they should be: by situation, not by brochure.
What lining actually is
Cured-in-place pipe (CIPP) lining inserts a resin-saturated felt or fibreglass sleeve into the existing pipe, inflates it against the walls, and cures it — with hot water, steam or UV light — into a new structural pipe inside the old one. A cousin technique, spray/brush coating, applies epoxy to the cleaned interior instead. Done properly on the right pipe, a cured liner is a genuine decades-class fix. The qualifier “on the right pipe” is doing heavy lifting in that sentence.
Where lining honestly wins
- Long buried runs where digging is the expensive part. A lateral running under a mature tree, an interlock driveway, an addition or a finished landscape — here excavation costs dominate, and a liner that avoids the dig can win the economics decisively. This is lining's home turf, covered further on the sewer line page.
- Pipe that is structurally intact but leaking at joints. A liner bridges cracked hubs and root-entry joints beautifully when the host pipe still holds its shape.
- Under-slab runs beneath finished basements, where breaking terrazzo or a heated floor multiplies replacement cost.
Where replacement wins
- The accessible vertical stack. A stack standing in a basement or a modest wall chase is the easiest pipe in the house to replace outright. Lining an accessible stack usually costs as much or more than replacing it — lining is priced per foot, and its economic advantage exists only where access is the problem.
- Heavily scaled, thin-walled cast iron. A liner needs a cleaned, sound host. Descaling 70-year-old pipe aggressively enough to line it sometimes finishes the job corrosion started — and a liner cured inside a collapsing host inherits the collapse.
- Pipe with bellies or back-pitch. A liner follows the host pipe's geometry exactly. Line a sagging pipe and you own a brand-new sagging pipe; only re-laying the run corrects grade.
- Already-narrow small-diameter branches. Every liner subtracts a few millimetres of bore. On a 4-inch main that's trivial; on an already-scaled 2-inch branch it can matter.
How to compare the two quotes like a professional
Get both on paper against the same camera footage, then check four things. Scope: does the lining quote include descaling and reinstating branch connections (each branch must be robotically cut back open after curing — ask how many)? Geometry: does the footage show bellies the liner would preserve? Warranty: what term, covering material and labour, and who honours it if the installer disappears? Whole-system logic: a lined lateral feeding an unlined dying stack — or the reverse — leaves half the problem in place; the cost page tiers help price the honest whole. When a lining pitch dodges the descaling question or quotes sight-unseen, that's your answer about the pitch, not necessarily the technology.