Pipe Installation

When can you close in a concealed gas line?

Only after inspection (Clause 6.22)

What are the minimum sizes and requirements for threaded gas piping?

Natural gas: Minimum 1/2" unless using Schedule 80 and class 300 malleable iron fittings

Propane: Can be less than 1/2" (as small as 3/8") only if it’s a branch line to a single appliance and ≤25ft (cannot be concealed if less than 1/2")

What types of joints and fittings are permitted on steel, copper, and plastic gas lines?

Steel pipe joints: threaded, flanged, welded, press-connect, compression type (Dresser)

Joints over 2": must be welded by a class B pressure welder

Pipe dope: must be approved for pressure/temp

Gaskets: synthetic only (no natural rubber)

Copper/steel tubing: flared (forged flare nuts), brazed (over 1000°F), double ferrule compression (Swagelok), or press-connect

Bushings: must be steel/malleable iron (aluminum only for valve installation), no nested bushings

What are the requirements for appliance connectors and quick disconnects?

Max flex length: 2ft (vented), 6ft (unvented)

Connectors cannot pass through any wall, ceiling, floor, or partition

Quick disconnect must have a gas cock immediately upstream (proper flow direction)

What is the preferred practice for piping outlets and pipe protrusions?

Preferred: install a gas cock with nipple and cap for future use

Pipe protruding from wall: minimum 1" unthreaded

From floor: minimum 2" unthreaded (allows for backing wrench)

What are the requirements for drip and dirt pockets?

Not required on risers

Required at bottom of final drop to appliance

Minimum depth: 3" or pipe diameter (whichever greater)

Nipple diameter: same as pipe served or 2" (whichever less)

What practices are prohibited in gas line installation?

Cannot use defective materials

Cannot nest bushings

Only field bend if using proper bender

No street tees, street elbows, or close nipples

No unions/swing joints in concealed locations

Cannot use piping/tubing for electricity or grounding (except appliance controls)

What are the requirements for underground piping/tubing?

Minimum 15" deep (24" if under driveway/parking)

If under >25ft of paving/concrete: requires vent or inspection sleeve

Plastic pipe: must have above-ground shutoff, tracer wire

Allowed joining: welding, compression, flared, or heat fusion

Must contact Utility Safety Partners before excavation

How do you protect piping/tubing from damage?

In corrosive atmosphere: paint/coat

Must move freely without abrasion

Tubing <1.75" from inside wall: must have striker plates

Plastic: protect from direct sunlight

Outdoor tubing near traffic: protect with posts/guardrails

How is gas piping/tubing identified in residential, commercial, and public installations?

Residential: every 6ft (painted yellow, yellow bands, or “gas/propane” markings)

Commercial: every 20ft (same options)

Public: APWA color code (gas = orange); any other color must be labeled every 20ft

Where must shutoff valves be installed and what are the rules?

On final drop or rise as close as possible to appliance

Residential: can be on horizontal finish piping if within 2ft of appliance

May be up to 50ft away if clearly labeled and accessible

Can be waived in some manifold installations (commercial/room heaters <50ft from furthest appliance)

0.5psig and 1” or larger: must be ball, eccentric, or lubricated plug valve

Required when piping/tubing extends from one building to another (at both exit and entry)

What are the rules for gas hoses and fittings?

Hose not allowed on vented appliances (except radiant tube heaters)

Allowed on unvented/mobile appliances

Hose cannot pass through walls

Permanent hose: max 10ft

Temporary (construction heater): 15-75ft

What are the requirements for rooftop gas piping/tubing?

Allow for expansion/contraction (Annex G)

Supported on treated wood block or approved supports

All threaded fittings must be individually supported

Tubing must be continuously supported

What is required for inspection of plastic gas systems?

Plastic materials and fusion joints must be inspected by qualified personnel before going into service

What is the maximum spacing for pipe hangers/supports?

1/2” or less, horizontal: 6ft

3/4” to 1”, horizontal: 8ft

1-1/4” to 2-1/2”, horizontal: 10ft

1-1/4” or larger, vertical: every floor, max 125% of horizontal spacing

All tubing: 6ft

Rule of thumb: leave 3/4”–1” space between pipe and structure

Can’t support by another pipe or appliance; hanger always at top of drop/riser

How is gas piping tested before service?

Test rough-in using air, CO₂, or inert gas (not gas)

Pressure/duration per Table 6.3, no drop allowed

Remove/replace devices that can’t withstand test pressure (e.g. remove regulator, insert spool piece)

Never pressure test against control valves

All shutoffs open during test

Min 15 psig for 15 min on rough-in

Finished piping never pressure tested—use soapy water & meter dial

Pressure gauge: min 3” diameter, 2 psig increments or 2% of max, max gauge range 15–300% over test pressure

Additions <20ft and <0.5psig may be soap tested only

How is gas line purged after testing?

Purge point vented ≥10ft from building/air intake/ignition sources

Competent person must attend

Valve with handle within 5ft of purge point; cannot use appliance shutoff

Large lines: purge with inert gas before introducing NG/propane

Small lines: may not require purge (see Table 6.4)

<400MBH appliances: purge to burner if not in combustion chamber

What is a standing pressure test and when is it used?

Test with only pilot running (downstream of service or 2nd stage reg, upstream of appliance reg)

Shows regulator adjustment

Typical values: MFG gas 6”wc, NG 7”wc, propane/butane 11”wc

What is an operating pressure test and when is it used?

Test with main burners at full fire (downstream of service reg, upstream of appliance reg)

Same location as standing pressure

Check pressure drop does not exceed Table 6.1 max:
  - NG 7”wc: max 1” drop
  - Propane/Butane 11”wc: max 1” drop
  - High-pressure NG/propane/butane: max 50% of gauge pressure

If over max, line is undersized

What is manifold pressure?

Pressure at the burner; typically NG 3.5”wc, propane/butane 11”wc (check appliance nameplate)

Who is responsible for leak checks and pressure tests?

The gasfitter is responsible for all checks and tests before service

When can a hose be used on a gas appliance?

Hose is permitted only for mobile or unvented appliances, not vented appliances

Where can plastic piping be installed for gas lines?

Plastic piping is only allowed for underground or outdoor gas line installations

Can girders, beams, or joists be cut for gas piping installation?

Yes, but you must consult with an engineer first

What is the purpose of a GSG plate (striker bar) in gas line installation?

A GSG plate (striker bar) is required when tubing is installed within 1.75” of the wall surface

On what appliances can a corrugated metal connector be used, and what is the max length?

Corrugated connectors are allowed on ranges, dryers, suspended, decorative, or room heaters, with a maximum length of 6ft

When is Type L or G copper tubing allowed underground?

Type L or G copper tubing can be used underground if coated with PVC or PE resin

When is a dirt pocket required on a gas line?

A dirt pocket is required on the final drop to an appliance, except for ranges and clothes dryers

What is the maximum size for a purge line used for purging a gas line up to 4” NPS?

The purge line must not be larger than 1/2” NPS for purging a line up to 4” NPS

What should be done after connecting a gas appliance to a line?

Check for leaks before turning on the gas

What pressure must factory-coated piping be tested to?

Factory-coated piping must be tested to a minimum of 100 psi