306A Pipe Joining and Fitting Methods 3

Question 1

When joining PEX-A tubing using the expansion method, what must be done immediately after the pipe end is expanded?

Accepted Answer

Assemble the fitting immediately — PEX-A has shape memory and will contract to grip the fitting barb as it warms

Answer

Cool the expanded tube in cold water before pushing onto the fitting

Answer

Expand the tube a second time to ensure a tighter fit before assembly

Answer

Chill the fitting in ice water to reduce its diameter for easier insertion

Question 2

Which type of fitting incorporates a sight (witness) hole that confirms the pipe has been fully inserted to the correct depth?

Accepted Answer

Push-fit (press-to-connect) fittings — the sight hole confirms full pipe insertion before the O-ring seals

Answer

Compression fittings — the witness hole is located in the ferrule body

Answer

Grooved (Victaulic) couplings — the sight hole confirms the groove depth is correct

Answer

Soldered copper fittings — the witness hole allows excess solder to escape during assembly

Question 3

What precautions should be taken when soldering a joint adjacent to an installed ball valve or gate valve?

Accepted Answer

Open the valve fully and use a wet rag as a heat sink between the torch flame and the valve body

Answer

Remove all valves completely before performing any soldering work nearby

Answer

Solder as quickly as possible and accept that some seal damage is inevitable

Answer

Fill the valve body with water through the packing gland before soldering begins

Question 4

What is the primary functional difference between a coupling and a union in a threaded steel piping system?

Accepted Answer

A union allows a section of pipe to be disconnected without rotating the pipe; a coupling requires the pipe to be turned during disassembly

Answer

A coupling is only for reducing pipe size; a union is for same-size connections

Answer

A union is approved for gas piping only; a coupling is used for water piping

Answer

There is no functional difference — both fittings are used interchangeably

Question 5

What does an electrofusion control unit supply when joining polyethylene (PE) gas pipe with electrofusion fittings?

Accepted Answer

A precise electrical current for a specified time to activate the resistance wire and fuse the pipe to the fitting

Answer

Mechanical clamping pressure to hold the pipe while an adhesive cures

Answer

UV light to cure a photosensitive bonding agent inside the fitting

Answer

Compressed air to thermally expand the fitting over the pipe end

Question 6

How many threads should remain visible outside a fitting after a properly wrench-tightened NPT threaded steel pipe joint?

Accepted Answer

Approximately 3 to 5 threads should remain visible outside the fitting

Answer

The pipe end should be flush with the fitting face — no exposed threads should remain

Answer

At least 8 full threads must remain outside for a properly rated connection

Answer

Thread count visible outside does not matter as long as PTFE tape or pipe dope is used

Question 7

Which joining method is NOT rated for pressurized copper water supply piping and therefore cannot be used on supply lines?

Accepted Answer

No-hub (Mission-type) banded rubber couplings — rated for drain, waste, and vent piping only, not pressure piping

Answer

Press (ProPress) fittings installed with an approved pressing tool

Answer

Soldered (sweat) joints made with lead-free solder and water-soluble flux

Answer

Approved push-fit fittings listed for use in concealed locations