Short definition
PVC pipe (rigid polyvinyl chloride) is the white or off-white thermoplastic used for cold-water supply, drainage / waste / vent (DWV), and irrigation. Available in Schedule 40 (residential standard) and Schedule 80 (industrial / threading-required), joined by a two-step solvent-cement process (purple primer plus PVC cement). Not rated for hot water — softens around 140°F.
What it is
PVC is the workhorse plastic of residential plumbing’s cold side. You’ll see it in the white drain pipes under sinks, in vent stacks running up through the attic, in irrigation manifolds and laterals, and in the cold-water mains of some new-construction homes (where allowed by local code).
The joining process is two-step: apply purple primer to clean both surfaces, apply PVC cement, and join with a quarter-turn twist. The primer chemically softens the surface; the cement bonds the softened layers; the result is a continuous welded joint, not a glued one. Skipping the primer is the most common DIY mistake — joints look fine but eventually weep at the bond line.
Why it matters to a homeowner
PVC is the standard DIY plastic for any cold-water or DWV repair. The big rule: PVC is not for hot water. Hot supply needs CPVC, copper, or PEX. Mixing the two plastics requires CPVC-specific cement on the CPVC side; using PVC cement on a CPVC joint produces unreliable bonds.
When a quote talks about “Sch 40 PVC drain replacement,” “PVC vent stack,” or “PVC irrigation manifold,” it’s the standard residential application.
Common variants and what PVC is not
- PVC vs. CPVC. PVC is cold only; CPVC is hot and cold rated. Different solvent cements.
- PVC vs. ABS. Both are DWV plastics. PVC is white, two-step cement; ABS is black, single-step cement. WA allows both; some jurisdictions allow only one.
- Schedule 40 vs. Schedule 80. Same OD, different wall thickness. Sch 80 is required for threaded joints.
Common failure modes
- Glue joint failure from skipped primer, dirty pipe, cold-weather application, or expired cement.
- Brittle fracture in cold installations — PVC gets fragile below about 40°F. (This is why PNW plumbers prefer ABS for unconditioned attic vents.)
- UV degradation on exterior vent terminations long-term — paint with latex or cover.
- Crushing under driveway or vehicle traffic where buried too shallow.
- Solvent-cement under-wetting on lower joints in long horizontal runs — air pockets prevent full surface wetting.