Copper tube and fittings are used for three types of systems installed in single-family dwellings and multi-storey residences. They are classified by pressure and are known as:

.. Less than 7" w.c. (1.75 kPa)

.. 7" up to 14" w.c. (1.75 to 3.5 kPa)

.. 2 psig (14 kPa)

w.c. = water column

psig = pounds per square inch gauge

The tube must be of sufficient size to provide a supply of gas to meet the requirements of volume and pressure at the point of use, and the designer of a system should consult with the company supplying the gas regarding the pressure available and the metering regulations. For some systems it might be found that a 2 psig (14 kPa) system is impractical and/or unnecessary, and that a lower pressure system is quite adequate and acceptable. The lower pressure system is preferred, but when sizing indicates tube sizes of 7/8" O.D. (3/4" nominal) or greater, consideration should be given to using a 2 psig (14 kPa) system and a smaller size of tube.

In a Less than 7" w.c. (1.75 kPa), or a 7" up to 14" w.c. (1.75 to 3.5 kPa) system, the gas pressure is sometimes, but not always, reduced by a regulator at the meter. In a 2 psig (14kPa) system, the gas is reduced to 2 psig (14kPa) by a regulator at the meter, and by another regulator or regulators, to give 7" water column in the distribution layout or at each appliance.

The differences in the capacities of the three systems may be noted by comparing the figures in the accompanying Tables, those in blue being in inch-pound units and those in yellow are metric. The heating value in BTUs per cubic foot (BTU/ft³) of a natural gas may vary with its source, hence the inch-pound Tables are in Thousands of BTU/h to provide a relationship with cubic feet per hour (ft³.h). In similar manner, the metric Tables are in kW, and the heating value of the gas in Mega Joules per cubic metre (MJ/m³), will provide the relationship with cubic metres per hour (m³/h). All Tables are based on gas with a relative density of 0.60 and adjustments should be made for gases of different densities. The Tables include a factor (F=1.2) to allow for a reasonable number of fittings.

Tables 1 and 2 are for systems of Less than 7" w.c. (1.75 kPa), based on a pressure drop of 0.5" w.c. (125 Pa). Tables 3 and 4 are for 7" up to 14" w.c. (1.75 to 3.5 kPa), based on a pressure drop of 1" w.c. (250 Pa). Tables 5 and 6 are for 2 psig (14 kPa) systems, based on a 1 psig (7 kPa) pressure drop, and Tables 7 and 8 for 2 psig (14 kPa) systems, based on a 1.5 psig (10kPa) pressure drop.

The type of system must be clearly identified with yellow paint or marking labels, as required by the regulatory authority. Examples of typical labels are shown on below. Identification marking is used on both sides of a wall, floor or partition, and at intervals usually not exceeding 6 ft. (2m) throughout the length of the tube runs.


Natural gas lines are identified with yellow paint or with marking labels similar to those above.

Copper systems may be added to existing steel pipe systems. In some cases, it might be more cost effective to install steel pipe to certain appliances, for example the furnace and water heater, and use copper for the drops to those appliances and for the runs to the other appliances, such as the range, dryer, fireplace and barbecue. When installing additional appliances to existing systems, care must be taken to ensure connection to a line supplying the proper pressure for the appliance controls. Direct venting of appliances, or induced draft fans, may assist in the location of an appliance and should be taken into consideration when choosing a system and designing its layout.



Copper may be added to existing steel pipe systems. This photo shows the transition and the copper line to a new outdoor barbecue.


Copper tube is available in long lengths of up to 100 ft. (30m), which reduces the number of joints in the system and speeds-up installation.


The compact dimensions of copper tube (compared here with its equivalent threaded steel pipe) and its flexibility, are factors leading to easier, better installations, at lower cost.


Domestic hot-water heaters grouped together in a mechanical room in a low-rise apartment building. Each tank has a designated apartment unit, its own copper gas feed from its own meter, and its own copper hot water lines to the plumbing fixtures.


A Magic-Pak gas-fired heating/air conditioning unit, connected to the duct systems for a classroom of a school. This concept allows individual temperature control for separate rooms or sections. The 1/2" O.D., copper tube at 2 psig, has a manual shut-off valve, then a regulator to reduce the pressure for the unit.


Above, the quick-connector of the flexible tube to a portable outdoor barbecue, and below, a sectional drawing of a gas fireplace. These two items, as well as being included in most new installations, are very popular add-on appliances. The inherent advantages of the copper system, simplify making such additions to both existing copper or steel installations.