Short definition
Pipe relining in its strict sense refers to spraying or centrifugally casting an epoxy resin coating inside an existing pipe to seal leaks and bridge small cracks. It forms a new internal coating, not a structural pipe-in-pipe. The industry sometimes uses “relining” loosely as an umbrella for CIPP, slip-lining, and epoxy spray; this entry is the strict, thin-coating definition.
What it is
The application method varies — a brush-applicator spinning down the pipe (centrifugally cast), a spray head pulled through, or filling the pipe and forcing epoxy through under pressure. All produce a thin, even epoxy layer inside the existing pipe. Cure times range from a few hours to a day depending on the resin and method.
The coating’s job is to seal — fill cracks, cover small areas of internal corrosion, restore a smooth flow surface. It does not bridge structural failures. The host pipe must remain structurally intact for the coating to do its work.
Why it matters to a homeowner
For small cast-iron stack pinholes inside a wall, epoxy relining can save the demolition cost of a full repipe. For pre-purchase scopes that show minor pinholes in a building drain, relining is sometimes a viable alternative to full replacement. Costs in WA: roughly $80–$200 per linear foot for residential spray relining — overlapping with CIPP cost but generally cheaper because there’s less material.
The trade-off is durability. Relining extends a pipe’s life by years to a couple of decades, depending on conditions. CIPP is structural and longer-lived. Pipe bursting gives you a brand-new pipe. The right choice depends on how many years of life you need and how much structural damage exists.
Common variants / not the same as
- Pipe relining (epoxy spray, thin coating) vs. CIPP (resin-saturated felt liner, thick structural layer). CIPP is structural. Relining is sealant. Both are sometimes called “relining” loosely; specs differ.
- Pipe relining vs. slip-lining. Slip-lining inserts a smaller pipe inside the old. Relining adds a coating to the existing pipe.
- Pipe relining vs. pipe bursting. Bursting replaces the pipe. Relining doesn’t.
Common failure modes / limits
- Cannot fix a fully collapsed or deformed pipe — no host wall to anchor coating to.
- Coating thickness insufficient for structural support — host pipe must remain structurally intact.
- Bond failure if pipe wasn’t cleaned thoroughly first — the coating peels and leaks.
- Limited to fairly straight runs.