I85PREP
⌘ K
Plumbing NC I study materials
Plumbing NC I study resources

Plumbing NC I: Pipe Cutting, Threading, Bending, and Joining Methods

Plumbing NC I · Work through your exam, one topic at a time.

All guide sections

Pipe Cutting, Threading, Bending, and Joining Methods

Cutting, threading, bending and joining

This domain tests whether you can join plumbing pipe by the method the material requires and test it only after the joint is ready. Questions often contrast PVC solvent cementing, GI threading, copper soldering or pressing, PPR heat fusion and cast-iron no-hub coupling.

Core rules

  • Cut square, deburr and chamfer where required. A burr restricts flow and can damage a gasket or die.
  • PVC and CPVC: clean the pipe and socket, apply primer, apply cement to both surfaces while wet, insert fully, quarter-turn and hold, wipe excess, then follow the manufacturer's cure schedule before pressure testing.
  • GI pipe: cut, ream, thread with the correct die and cutting oil, check the NPT taper of about 1:16, apply jointing compound or tape to the male thread, and tighten without cross-threading.
  • Copper: cut, ream, clean, flux and solder with lead-free solder, or use the correct press jaw and complete the stroke. Protect nearby surfaces from heat.
  • PPR: heat both pipe and fitting to the specified depth and time, join without rotating, and hold until set.
  • Cast iron: use the correct no-hub coupling and torque; do not substitute a flexible coupling where the specification requires a restrained joint.
  • Bending: use the correct spring or bender, respect the minimum bend radius, and do not kink the pipe.

Worked example

Join 25 mm PVC water pipe. Reasoning: cut square with a fine-tooth saw; chamfer the end about 15 degrees; clean the end and socket; apply purple primer; apply cement while the primer is still wet; insert fully with a quarter turn; hold for about 30 seconds; wipe the bead; allow the manufacturer's cure time before hydrostatic testing. Pressure testing immediately is the usual cause of joint failure.

Traps

Skipping primer, using too much cement, failing to chamfer, cross-threading GI joints, overheating PPR, and testing before cure are common. A soldered joint that looks bright is not proof of full penetration; check the solder line.