306A Pipe Joining and Fitting Methods 2 — Questions and Answers
Question 1: When joining ABS or PVC drain pipe with solvent cement, what motion is used when inserting the pipe into the socket?
- Rotate the pipe continuously while pushing it in to spread the cement evenly
- Give the pipe a quick quarter-turn while pushing to full depth, then hold without rotation (Correct answer)
- Push the pipe straight in with no rotation and hold for 30 seconds
- Rotate the pipe one full clockwise turn before pushing to socket depth
Correct answer: Give the pipe a quick quarter-turn while pushing to full depth, then hold without rotation
A quarter-turn during insertion distributes the cement evenly across the bonding surfaces and achieves correct alignment; holding the joint prevents it from backing out while the cement sets.
Question 2: What is the correct sequence of operations when cutting and threading steel pipe on a power threading machine?
- Thread the pipe first, then cut to length, ream, and apply sealant
- Cut to length, ream the inside, thread, apply sealant, then assemble (Correct answer)
- Cut to length, thread, then ream the inside, apply sealant
- Ream first, cut to length, thread, then apply sealant
Correct answer: Cut to length, ream the inside, thread, apply sealant, then assemble
Cutting first ensures proper length; reaming after cutting removes the internal burr created by the pipe cutter; threading follows reaming, and sealant is applied just before assembly.
Question 3: What is the approximate pressure rating of 1-inch Schedule 40 PVC pipe at 23°C for cold water service?
- Approximately 1,380 kPa (200 psi) regardless of temperature
- Only 345 kPa (50 psi) for any PVC installation
- Approximately 690 kPa (100 psi), with the rating decreasing as temperature rises (Correct answer)
- PVC Schedule 40 has no pressure rating and cannot be used for supply lines
Correct answer: Approximately 690 kPa (100 psi), with the rating decreasing as temperature rises
Schedule 40 PVC is rated near 690 kPa (100 psi) at room temperature, but this rating drops significantly with increasing temperature, which is why it cannot be used on hot water supply lines.
Question 4: When soldering a copper fitting, where should the heat from the torch primarily be directed?
- To the solder wire directly, melting it so it drips into the joint
- To both the pipe and fitting equally and simultaneously
- To the fitting body, allowing capillary action to draw solder fully into the joint (Correct answer)
- To the pipe only, well away from the fitting body
Correct answer: To the fitting body, allowing capillary action to draw solder fully into the joint
Heating the fitting body warms the entire joint assembly so that when solder contacts the pipe-fitting interface, capillary action pulls the molten solder completely into the gap.
Question 5: In which direction should PTFE thread tape be wound around male pipe threads before making a connection?
- Clockwise when viewed from the threaded pipe end, in the direction of thread engagement (Correct answer)
- Counter-clockwise when viewed from the threaded pipe end
- Direction is irrelevant as long as the tape is applied tightly
- PTFE tape must never be used — only liquid pipe sealant is acceptable on threaded joints
Correct answer: Clockwise when viewed from the threaded pipe end, in the direction of thread engagement
Applying PTFE tape clockwise (in the direction the fitting will be threaded on) ensures the tape seats into the threads during assembly rather than unravelling as the fitting is tightened.
Question 6: What is the minimum cure time before a solvent-cemented CPVC hot water line may be pressure tested in warm conditions (above 15°C)?
- 5 minutes — CPVC solvent cement achieves full strength almost instantly
- Follow manufacturer specifications — typically a minimum of 1 hour before low-pressure test and 24 hours before full system pressure (Correct answer)
- 72 hours minimum regardless of temperature or pipe size
- No cure time required; CPVC joints may be pressure tested immediately after assembly
Correct answer: Follow manufacturer specifications — typically a minimum of 1 hour before low-pressure test and 24 hours before full system pressure
Solvent cement creates a chemical weld that requires initial set time before handling and full cure before pressure testing; premature pressurization will cause joint failure.
Question 7: Which type of coupling allows pipes of different outer diameters or materials to be joined in a drain system without threading or solvent cement?
- A standard PVC socket coupling with solvent cement
- A grooved (Victaulic-type) coupling that requires precision-machined grooves on both pipes
- A compression fitting with a brass ferrule and compression nut
- A banded rubber (Mission/no-hub-type) coupling with stainless steel clamp bands (Correct answer)
Correct answer: A banded rubber (Mission/no-hub-type) coupling with stainless steel clamp bands
Banded rubber couplings use a flexible neoprene sleeve and stainless steel bands to join pipes of differing sizes or materials, making them ideal for connecting new plastic pipe to existing cast iron or clay sewer pipe.
306A Pipe Joining and Fitting Methods 2
When joining ABS or PVC drain pipe with solvent cement, what motion is used when inserting the pipe into the socket?