What Is a Cap Used For in Plumbing?
A plumbing cap comes in many different materials (black malleable, galvanized, copper, pvc, cpvc, and more...) is a fitting used to close off the end of a pipe or fitting. Its main function is to:
Caps install over or onto the end of a pipe:
A plumbing cap comes in many different materials (black malleable, galvanized, copper, pvc, cpvc, and more...) is a fitting used to close off the end of a pipe or fitting. Its main function is to:
- Seal a pipe end
- Stop water, gas, or air flow
- Terminate or temporarily block a line
- Permanently closing an unused pipe
- Temporarily sealing a line during renovations
- Capping future branch connections
- pressure testing a plumbing system
- Isolating abandoned fixtures or appliances
Caps install over or onto the end of a pipe:
- Threaded Cap – Screws onto male pipe threads
- Slip / Socket Cap (PVC or Copper) – Glued or soldered over pipe
- Press Cap – Pressed onto copper pipe with a press tool
- Push-to-Connect Cap – Pushes onto pipe (temporary or permanent)
- Once installed, the cap creates a watertight or airtight seal.
Common Materials
- PVC / CPVC
- Copper
- Brass
- Galvanized
- Black malleable iron
- Stainless steel
Simple Example
You remove an old sink but plan to add one later. You install a ½" threaded cap on the water line so the rest of the system can stay pressurized.
In Plain English
A plumbing cap is used to close off the end of a pipe so nothing can flow through it.