306A Pipe Joining and Fitting Methods 1 — Questions and Answers
Question 1: What type of solder is required for copper joints in potable water systems under the National Plumbing Code of Canada?
- Lead-free solder containing no more than 0.2% lead (Correct answer)
- 50/50 tin-lead solder
- Silver solder only
- 60/40 lead-tin solder
Correct answer: Lead-free solder containing no more than 0.2% lead
The National Plumbing Code of Canada requires lead-free solder to prevent lead contamination in potable water systems.
Question 2: After cutting rigid PVC pipe with a hacksaw for a solvent-cemented joint, what must be done to the pipe end before applying primer?
- Apply solvent cement before deburring to seal the saw marks
- Deburr and chamfer the pipe end to ensure full insertion and avoid scraping cement from the socket (Correct answer)
- Heat the pipe end with a heat gun to smooth the cut surface
- Sand the outside only without touching the pipe bore
Correct answer: Deburr and chamfer the pipe end to ensure full insertion and avoid scraping cement from the socket
Deburring and chamfering removes sharp edges that would scrape cement from socket walls and ensures the pipe seats to full depth for a strong solvent bond.
Question 3: What is the standard taper for NPT (National Pipe Taper) threads used on steel pipe fittings?
- 1 in 8 measured on the pipe diameter
- 1 in 16 measured on the pipe diameter (3/4 inch per foot) (Correct answer)
- 1 in 12 measured on the pipe diameter
- 1 in 32 measured on the pipe diameter
Correct answer: 1 in 16 measured on the pipe diameter (3/4 inch per foot)
NPT threads have a standardized taper of 1 in 16 on the diameter, creating the wedging interference fit that seals the joint.
Question 4: When making a crimp-ring connection on PEX tubing, which tool verifies that the crimp ring has been correctly compressed?
- A torque wrench set to manufacturer specification
- Visual inspection of the crimp ring profile only
- A go/no-go gauge that measures the outer diameter of the crimped ring (Correct answer)
- A micrometer to measure the pipe wall thickness after crimping
Correct answer: A go/no-go gauge that measures the outer diameter of the crimped ring
A go/no-go gauge checks that the compressed crimp ring diameter falls within the specified range, confirming the connection is neither under- nor over-crimped.
Question 5: Which type of flux must NOT be used when soldering copper pipe in a potable water system?
- Acid (active) flux containing zinc chloride (Correct answer)
- Lead-free water-soluble flux
- Petroleum-based non-acid flux approved for plumbing
- No-clean flux approved for copper water piping
Correct answer: Acid (active) flux containing zinc chloride
Acid flux contains zinc chloride which is corrosive and toxic; residue left inside a pipe would contaminate drinking water and accelerate internal corrosion.
Question 6: When connecting copper pipe directly to a galvanized steel fitting, what type of connector prevents galvanic corrosion at the joint?
- A standard brass coupling
- A threaded brass nipple with PTFE tape
- Direct threaded connection sealed with pipe dope is acceptable
- A dielectric union that electrically isolates the two dissimilar metals (Correct answer)
Correct answer: A dielectric union that electrically isolates the two dissimilar metals
A dielectric union separates copper and galvanized steel with a non-conductive barrier, interrupting the galvanic cell that would otherwise cause accelerated corrosion at the joint.
Question 7: When preparing copper pipe for a push-fit (SharkBite-type) fitting, what is the most critical preparation step?
- Cutting the pipe square and removing all burrs from the pipe end (Correct answer)
- Applying flux to the pipe end before insertion
- Bevelling the pipe end at 45 degrees for easier insertion
- Pre-heating the fitting body to expand it before inserting the pipe
Correct answer: Cutting the pipe square and removing all burrs from the pipe end
A square, burr-free pipe end allows the O-ring inside the fitting to seal uniformly around the pipe circumference; burrs or an angled cut cause leaks.
306A Pipe Joining and Fitting Methods 1
What type of solder is required for copper joints in potable water systems under the National Plumbing Code of Canada?