306A Gas Piping Systems 1 — Questions and Answers
Question 1: What is the standard test pressure for a residential natural gas piping system in Canada?
- 15 kPa (2.2 psi) for 10 minutes
- 35 kPa (5 psi) for 15 minutes with no pressure drop (Correct answer)
- 100 kPa (14.5 psi) for 30 minutes
- 200 kPa (29 psi) for 1 hour
Correct answer: 35 kPa (5 psi) for 15 minutes with no pressure drop
Residential natural gas piping is typically tested at 35 kPa (5 psi) using air or inert gas for a minimum of 15 minutes with no measurable pressure drop. This is significantly above operating pressure to reveal any leaks.
Question 2: What is the normal operating pressure for natural gas in a residential system?
- 0.5 kPa (2 inches WC)
- 1.75 kPa (7 inches WC) (Correct answer)
- 3.5 kPa (14 inches WC)
- 14 kPa (2 psi)
Correct answer: 1.75 kPa (7 inches WC)
Natural gas in residential systems is delivered at approximately 1.75 kPa (7 inches of water column). The gas utility regulates the pressure down to this level at the meter.
Question 3: What method must be used to detect gas leaks in piping?
- A lit match or lighter
- An approved combustible gas detector or soapy water solution applied to joints (Correct answer)
- Visual inspection only
- Listening for hissing sounds only
Correct answer: An approved combustible gas detector or soapy water solution applied to joints
Gas leaks must be detected using an approved combustible gas detector or by applying a soap-and-water solution to joints and connections. Bubbles indicate a leak. Never use an open flame to check for gas leaks.
Question 4: What pipe material is most commonly used for interior residential natural gas piping in Canada?
- Copper Type L
- Black steel (iron) pipe (Correct answer)
- PVC pipe
- Galvanized steel pipe
Correct answer: Black steel (iron) pipe
Black steel (iron) pipe with threaded fittings is the most common material for interior natural gas piping. It is strong, durable, and approved for gas service. Galvanized pipe is not recommended because the zinc coating can flake off and clog gas valve orifices.
Question 5: What is a 'drip leg' (sediment trap) on a gas line and where is it required?
- A filter on the gas meter
- A vertical section of pipe with a cap at the bottom, installed at each gas appliance connection to catch moisture and debris before it enters the appliance (Correct answer)
- A device to reduce gas pressure
- A noise-reducing fitting in the gas line
Correct answer: A vertical section of pipe with a cap at the bottom, installed at each gas appliance connection to catch moisture and debris before it enters the appliance
A drip leg (sediment trap) is a short vertical pipe section with a cap, installed at the gas appliance connection point. It catches moisture, dirt, and pipe scale that could damage the appliance gas valve or clog the burner orifices.
Question 6: What is the minimum pipe size for a gas supply line serving a single residential appliance such as a furnace?
- ¼ inch
- ⅜ inch
- ½ inch (Correct answer)
- ¾ inch
Correct answer: ½ inch
The minimum gas supply pipe size is ½ inch for a single residential appliance. The actual size required depends on the appliance's BTU input rating, the length of the pipe run, and the number of fittings.
306A Gas Piping Systems 1
What is the standard test pressure for a residential natural gas piping system in Canada?