Plumbing Pipes Guide: CPVC vs PVC vs GI
Plumbing pipe material matters more than it might seem, since different materials are suited to different uses — hot versus cold water, pressure levels, and exposure conditions — and using the wrong one in the wrong place is a genuine source of later plumbing problems.
CPVC (Chlorinated Polyvinyl Chloride)
CPVC is commonly used for both hot and cold water supply lines, since it handles higher temperatures better than standard PVC without degrading. It's lightweight, resistant to corrosion, and has become a common modern default for indoor water supply plumbing in residential construction.
PVC (Polyvinyl Chloride)
Standard PVC is widely used for drainage, waste, and vent (DWV) plumbing, and for cold water applications, but it's not rated for hot water use — using PVC where hot water will run through it can lead to pipe degradation and failure over time. This distinction matters, and it's worth confirming your contractor isn't using PVC where CPVC is actually needed.
GI (Galvanized Iron) pipes
GI pipes were the traditional standard for water supply for decades, offering good strength, but they're more prone to internal corrosion over time compared to modern plastic alternatives, which can affect water quality and eventually reduce flow through the pipe. GI is less commonly specified as the primary supply line in new residential construction today, though it's still used in some specific applications.
What to specify for a new home
- ✦Hot and cold water supply lines — CPVC is a common, well-suited modern choice
- ✦Drainage and waste lines — PVC (of appropriate diameter and grade) is standard
- ✦Confirm pipe wall thickness/pressure rating (schedule) matches your building's actual water pressure conditions, not just the material type alone
Why proper installation matters as much as material choice
Even the correct pipe material fails prematurely if joints are poorly solvent-welded (for CPVC/PVC) or if pipes are laid without proper support and slope for drainage lines. Ask your contractor to confirm proper installation practice, not just the material specification, since installation quality is where many real plumbing problems actually originate.
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Frequently Asked Questions
Can I use PVC pipes for hot water supply to save cost?+
This isn't recommended — standard PVC isn't rated for hot water temperatures and can degrade and fail over time when used this way. CPVC is the appropriate material for hot water supply lines.
Are GI pipes still used in modern construction?+
Less commonly as the primary water supply line compared to a few decades ago, given corrosion concerns over time, though they're still used in certain specific applications. CPVC has become a more common default for supply lines in new residential construction.
How do I know if my plumbing joints were installed correctly?+
This is difficult to verify visually once pipes are concealed in walls or under flooring — ask your contractor to confirm proper solvent welding or jointing practice was followed, and consider a pressure test before final concealment as an added verification step.
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