G3 Piping and Tubing Systems 3 — Questions and Answers
Question 1: How is residential gas piping sized?
- All residential piping is the same size
- Using pipe sizing tables based on BTU load, length, and allowable pressure drop (Correct answer)
- The gas utility determines sizes
- Sized to match meter outlet throughout
Correct answer: Using pipe sizing tables based on BTU load, length, and allowable pressure drop
Piping is sized using code tables considering demand, length, and pressure drop.
The allowable pressure drop from meter to furthest appliance is typically 0.5 inches water column.
Question 2: What is the difference between black iron and galvanized pipe for gas?
- Identical products with different names
- Black iron is approved; galvanized is not used due to flaking (Correct answer)
- Galvanized is preferred for all gas
- Black iron is outdoor only
Correct answer: Black iron is approved; galvanized is not used due to flaking
Black iron is standard for gas. Galvanized zinc coating can flake and clog components.
Zinc flakes can clog gas valve orifices, burner ports, and control components.
Question 3: What is the maximum allowable pressure drop in residential gas piping?
- 0.3 inches water column
- 0.5 inches water column (Correct answer)
- 1.0 inch water column
- 2.0 inches water column
Correct answer: 0.5 inches water column
Maximum is 0.5 inches WC from meter outlet to furthest appliance.
With 7 inches WC at the meter, a 0.5 inch drop still leaves sufficient appliance pressure.
Question 4: How should gas piping penetrations through walls be handled?
- Pipe passes directly without protection
- Pipe must be sleeved with an approved protective sleeve (Correct answer)
- A shutoff valve at each penetration
- Penetrations are not permitted
Correct answer: Pipe must be sleeved with an approved protective sleeve
CSA B149 requires protective sleeves at wall, floor, and ceiling penetrations.
The sleeve should be at least one pipe size larger, with below-grade penetrations sealed.
Question 5: What is the purpose of an appliance shutoff valve?
- To regulate gas pressure
- To allow gas isolation for servicing or emergency shutdown of individual appliances (Correct answer)
- To filter debris
- To measure gas flow
Correct answer: To allow gas isolation for servicing or emergency shutdown of individual appliances
It allows individual appliance gas supply to be turned off without affecting others.
CSA B149 requires one within reach of each appliance, accessible and hand-operable.
Question 6: What leak detection method is used after completing a gas piping installation?
- Listening for hissing only
- Applying approved leak detection solution to all joints and connections (Correct answer)
- Smelling for gas at each connection
- Using a thermal camera
Correct answer: Applying approved leak detection solution to all joints and connections
Approved soap bubble solution is applied to visually identify leaks at pressurized connections.
Electronic gas detectors may supplement but not replace bubble testing.
G3 Piping and Tubing Systems 3
How is residential gas piping sized?