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Copper Tube

Copper is the most commonly used material for residential water supply lines.

Because of its thinwall construction, copper tubing is smaller than IPS pipe. That distinguishes CTS (Copper Tubing Size) from IPS (Iron Pipe Size).

Threaded copper pipe is manufactured in IPS sizes for other industries but not for residential plumbing. Homeowners use the terms "Pipe" and "Tubing" interchangeably, but plumbing professionals do not.

There are two basic kinds of copper tube: hard (tempered) and soft (annealed).

Hard tubing is rigid tubing sold in lengths of 10 or 20 ft. and is the most common pipe installed in new homes. It makes a neater installation, but it is more difficult to install than soft tubing, particularly in existing homes. It needs very little mechanical support to keep it in position, compared to soft tubing.

Soft copper tubing is sold in coils of 60 to 100 ft. and is often preferred for repair work since it can be run around obstacles without connections or cuts. Both function equally well once installed.

Copper pipe is available in three basic types:

• Type M
  is a thin walled pipe. It is the most common type of copper tube sold, used mainly behind walls inside homes to route water from the service line and water heater to the fixtures. Trunk lines are typically run in 3/4-in. type M copper with 1/2-in. type M branching away to serve individual fixtures.
  
  
• Type 'L' (hard or soft)
  for thicker wall tube, considered standard piping for use for water services inside and out, especially outside or wherever the pipe will be exposed.
  
  
• Type 'K' (hard or soft)
  the thickest, used mainly between water mains and the meter, for heavy-duty vacuum pump lines and underground lines.
  
  

Type 'L' is preferred by some contractors for home use. Local codes will dictate which type of pipe is required for the work being planned. Copper is very durable and lasts for many years. It is usually connected by soldering or sweating.

Fig. 1 shows the inside and outside dimensions of Type L copper tube.

Copper tube is also sold in larger sizes for DWV lines in 20 ft lengths (hard). Some plumbing contractors prefer it to PVC and some special situations require it.

Copper tube can be cut with a regular hacksaw but tube cutters are preferred because they ensure a square cut every time.

A jig or miter box should be used when cutting copper tube with a hacksaw to guarantee a square cut. When using a tube cutter, the copper tubing should be held in place with a pipe vise or a similar device. After the cut is made, any burrs inside the tube should be removed with a half-round file. A pipe cutter usually leaves more burrs than a hacksaw.

Copper is neither threaded nor welded, but is connected by solder in socket weld joints, using a process called 'sweating'.

Often, the fittings that are soldered to the tube have threaded ends, but the tube itself does not. Smaller diameter tubing is connected with compression fittings where a compression nut is slid onto the tubing over a small ring and then screwed to a fitting. The nut causes the ring to compress onto the tube between the nut and the fitting and seal the joint. No solder is used, and the joint may be disconnected with a wrench without cutting the tubing.

In most markets, copper tube is marginally more expensive than plastic pipe, but in a typical house the difference between choosing one over the other would only amount to a few hundred dollars, a small percentage of the overall construction budget. Copper plumbing is not always more expensive, though. It's the least expensive of all materials approved for gas-distribution piping. For water distribution systems, some are of the opinion that the labor costs to install copper are greater than that for PVC, but that depends on the experience of the tradesman.

Since copper tube became the standard for potable water systems, it has generally outlasted the buildings in which it has been installed and it's frequently recycled for new construction. Records show that corrosion failures of copper plumbing systems occur in less than 1 percent of all known installations. Copper discolors when it comes in contact with certain minerals, but this rarely results in a weakening of tube walls or joints. Minerals dissolved in the water in certain locales sometimes form scaling on tube walls, but that is generally attributable to the quality of the water itself and not to the nature of copper.

Copper should not be installed if the water has a PH of 6.5 or less, as this could cause copper to corrode, although this is a rare occurrence. The majority of public utilities supply water at a PH between 7.2 and 8.0. Private well water systems often have a PH below 6.5. When this it the case, it is suggested that a treatment system be installed to make the water less acidic.

Copper tube qualifies for use in residential water systems under NSF Standard 61 and also under all other widely used standards and codes.

The Safe Drinking Water Act, as amended in 1986, set lead content limits for pipes, fittings, solders and plumbing fixtures. Because of this, the use of lead solder in potable water systems has not been allowed for more than a decade.

See Also:

Other:
    ASTM Reference Library (material and manufacturing specifications)

Links to Related Websites:
Copper Development Association
Copper Tube Handbook.

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