Short definition
CPVC pipe (chlorinated polyvinyl chloride) is cream- or tan-colored rigid plastic supply pipe rated for both hot and cold potable water — up to about 210°F at 100 psi. It’s joined by a CPVC-specific solvent cement (PVC cement won’t work) and is NSF-61 listed for drinking water. Less common than PEX in modern Washington construction, but still found in 1980s–2000s installs.
What it is
CPVC was the rigid-plastic supply alternative to copper before PEX took over the market. Standard residential CPVC is sized to copper tube size (CTS) in SDR 11 wall thickness, which means it slips into the same fittings, valves, and stub-out spacing as copper. Industrial CPVC also exists in Schedule 40 and 80 wall thicknesses, but those aren’t common in homes.
The joining method matters: CPVC needs a CPVC-specific solvent cement. Regular PVC cement looks similar but has the wrong solvent profile and produces unreliable joints. Buying the right cement for the pipe is the single most common DIY mistake with CPVC.
Why it matters to a homeowner
If you bought a 1990s or early-2000s Washington home, your supply piping might be CPVC. Two things to know:
- Brittleness in cold spaces. CPVC is more brittle than PVC and is especially vulnerable to impact in cold attics, garages, and crawlspaces. A workman bumping a line, or a sharp freeze on an inadequately insulated run, can crack the pipe or a fitting. Multiple slow leaks at fittings are a common pattern in 1990s CPVC homes.
- Chemical incompatibility. Some plasticizers, foam insulations, and oils degrade CPVC. Read the labels before insulating, sealing, or sleeving CPVC pipe — the wrong product in contact can cause stress cracking over time.
In a repipe, CPVC is generally being replaced with PEX. Modern Washington plumbers rarely choose CPVC for new installs.
Common variants and what CPVC is not
- CPVC vs. PVC. PVC is rated for cold water and DWV only. CPVC is rated for hot and cold supply. They look similar (PVC white, CPVC tan/cream). Different solvent cements.
- CPVC vs. PEX. CPVC is rigid, joined by solvent welding; PEX is flexible, joined by crimp, clamp, or expansion. PEX has largely replaced CPVC in new WA residential.
- CTS vs. Schedule 40/80. Residential CPVC is CTS (SDR 11). Schedule 40/80 CPVC is industrial.
Common failure modes
- Brittle fracture from impact in unconditioned spaces.
- Glue joint failure from incorrect or aged solvent cement.
- Chemical incompatibility with certain plasticizers, foams, and oils — leads to stress cracking.
- UV degradation if exposed to sunlight.