Gas Piping & Installation
Piping materials, sizing, supports, CSST bonding, thread sealants, unions, flexible connectors, and concealed piping requirements.
- Select approved piping materials for gas installations
- Apply pipe sizing tables from CSA B149.1
- Install CSST with proper bonding requirements
- Use correct thread sealants and connection methods
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Piping Materials & Sizing Tables
Approved Piping Materials
CSA B149.1 specifies approved materials for gas piping:
| Material | Application | Notes |
|---|---|---|
| Black steel pipe | Most common for interior gas piping | Threaded or welded joints |
| CSST (Corrugated Stainless Steel Tubing) | Flexible gas piping | Requires bonding per CEC Part I |
| Copper tubing (Type K or L) | Some jurisdictions allow for interior | Flared fittings only, no solder |
| Polyethylene (PE) | Underground exterior only | Never inside buildings |
| Press-connect fittings | Gas piping up to NPS 4 | Must be certified for gas service (B149.1:25) |
Pipe Sizing
Gas pipe must be sized to deliver adequate gas volume at proper pressure to all connected appliances. Sizing depends on:
- Total BTU load of all appliances
- Pipe length from the meter to the farthest appliance
- Supply pressure available
- Pipe material and internal diameter
Sizing Tables
CSA B149.1 contains pipe sizing tables that list the maximum BTU capacity for each pipe size at various lengths. The exam may require you to use these tables to determine the correct pipe size for a given installation.
Press-Connect Fittings for Gas Piping
CSA B149.1:25 (in force March 2026) permits certified press-connect fittings for gas piping up to NPS 4. Press-connect fittings use a mechanical ring that is compressed onto the pipe with a specialized tool, creating a gas-tight seal without threading, soldering, or welding.
Press-Connect Certification Required
Only press-connect fittings bearing a valid certification mark for gas service may be used. The certification must confirm compliance with applicable CSA standards. Standard plumbing press-connect fittings are not approved for gas service - verify the fitting's certification before installation. The press-connect tool must also be the correct model for the fitting system being used.
Black steel pipe is the most common gas piping material. Pipe sizing must account for total BTU load, pipe length, and supply pressure. Use CSA B149.1 sizing tables to determine correct pipe diameter. CSA B149.1:25 now also permits certified press-connect fittings up to NPS 4 for gas piping applications.