G3 Piping and Tubing Systems 2 — Questions and Answers
Question 1: What is the standard test pressure for new residential gas piping?
- 3 psi
- 7 psi
- 15 psi (Correct answer)
- 50 psi
Correct answer: 15 psi
The standard is 15 psi, well above normal operating pressure of about 0.25 psi.
The test must hold for a specified duration with no pressure drop before the system is put into service.
Question 2: What type of pipe thread sealant is approved for gas connections?
- Standard white Teflon tape
- Yellow Teflon tape or approved gas-rated pipe dope (Correct answer)
- Any silicone sealant
- No sealant needed
Correct answer: Yellow Teflon tape or approved gas-rated pipe dope
Only sealants rated for gas service should be used, such as yellow Teflon tape.
Gas-rated yellow PTFE tape is denser and thicker than standard white plumber's tape.
Question 3: What is a drip leg (sediment trap) on a gas line?
- Drains condensation from gas supply
- Collects moisture, dirt, and debris before they reach appliance controls (Correct answer)
- Reduces gas pressure
- Provides a gauge connection point
Correct answer: Collects moisture, dirt, and debris before they reach appliance controls
A drip leg collects contaminants that could damage the gas valve.
CSA B149 requires one at each appliance connection, typically minimum 3 inches long.
Question 4: What is CSST and its special installation requirement?
- Copper Semi-Soft Tubing; silver brazing
- Corrugated Stainless Steel Tubing; proper bonding/grounding (Correct answer)
- Carbon Steel Standard Tubing; threading
- Certified Safety Standard Tubing; double-wall
Correct answer: Corrugated Stainless Steel Tubing; proper bonding/grounding
CSST is flexible gas piping requiring electrical bonding to protect against lightning.
Lightning can burn holes through the thin corrugated wall without proper bonding.
Question 5: What is the minimum burial depth for underground gas piping in Ontario?
- 6 inches
- 12 inches
- 18 inches (450 mm) (Correct answer)
- 36 inches
Correct answer: 18 inches (450 mm)
CSA B149 requires 18 inches (450 mm) below finished grade.
Greater depth may be required under vehicular traffic areas, plus warning tape above.
Question 6: Why must gas piping be properly supported at specified intervals?
- For aesthetics only
- To prevent sagging, joint stress, and potential leaks from movement (Correct answer)
- To make piping easier to paint
- Only required in commercial buildings
Correct answer: To prevent sagging, joint stress, and potential leaks from movement
Proper support prevents sagging, joint stress, and movement-caused leaks.
Supports must be compatible with pipe material to avoid galvanic corrosion.
G3 Piping and Tubing Systems 2
What is the standard test pressure for new residential gas piping?