All four classes of tubing can be used with the capillary solder system. The choice of tubing will depend on the nature of the work to be performed. If tubes are to be laid underground then Class 2 should be used.

Class 0 is recommended for all above ground work as its use would provide the maximum cost saving benefit. It is emphasized that Class 0 tubing is hard drawn and any change of direction should be made with fittings. Local annealing of Class 0 in order to produce a bend is not recommended.

When compared with traditional systems, capillary systems can realize an installation time saving of up to 70%.

SANS 460 Class 1 and 2 all have excellent bending qualities. There are various bending machines on the market and those with inner and outer formers make the best bends. Care should be taken when bending the Class 1 tube as it has a thin wall. The cheaper hand benders and springs do not perform satisfactorily on this class of tube.

Half hard tubes bent by hand should have a radius of at least 6 times the outside diameter of the tube and machine bent tubes should have a radius of not less than 3 times the outside diameter of the tube. Any deviation from the above figures could cause a restriction in the tube producing turbulent flow and the possibility of erosion corrosion.

It is most important to remember that SANS 460 Class 0 (hard drawn tube) should NOT be bent under any circumstances. Class 0 tube is ideally suited for use with capillary fittings, however, compression fittings should be avoided where possible. The use of a 90° or 45° capillary soldered elbow will provide a quick, inexpensive and neat bend.

Copper tubing, due to the very smooth bore, maintains excellent flow characteristics as there is less chance of furring than with traditional materials.

Because of copper tube’s excellent internal corrosion resistance, tube bores remain smooth and internal diameters constant, thus eliminating the need to account for bore reduction or roughening when computing friction losses as with steel piping.

Copper’s light weight facilitates shipment, fabrication and installation. When comparing steel pipe systems, weight reductions of up to 50% are afforded by copper systems. This is significant in terms of hanger requirements and dead loads imposed on supporting structural elements.

Copper is compatible with all types of piping. It is accepted practice to join copper tubing to galvanized piping provided that the copper is downstream from the galvanized pipe. Certain corrosion problems may be experienced under specific conditions if the copper tube is connected upstream.

When cutting copper tube with tubing cutters or a hacksaw, care should be taken to produce a square end and to remove the burr produced. This will remove the possibility of turbulent flow which could promote erosion corrosion.

Although variations in climatic temperatures are not as extreme in South Africa as they are, for example, in certain northern European countries, there are areas in this country where burst pipes due to winter freezing are not uncommon.

According to London-based metallurgical consultants, Clifford Breckon Limited, the layout of the plumbing system, particularly with regard to such things as the position of the fittings and the point of exposure to the lowest temperature, will affect the tendency of the system to freeze.

It is preferred practice not to lag each pipe individually in the roof, but to place the pipes below the ceiling lagging, which would protect the pipes from any draughts. At the same time, the warm air rising from the room below would be trapped in the space between the ceiling and the lagging where the pipes are situated.

Freezing itself does not necessarily mean that the pipes will burst. It is not the distension of the tubes by the ice which will cause a burst, but rather its distension by the water under pressure which causes the problem. Bursting, for example, does not occur at the first part to freeze, on the contrary, bursting invariably occurs where the water is still present as a liquid and usually, therefore, one of the last parts of the system to actually freeze. The pressure to produce bursting is generated by the change from water to ice and if the coldest point is in the middle of a straight length so that a plug of ice is first formed at this point with say, a fitting or stop tap at one side, then the chances are that the plug of ice will be moved along the tube by the pressure rather than a pressure build-up occurring.

The effect of pressure is to depress the freezing point slightly, so that under a mild frost nothing would happen in the case of a smooth bore copper tube. On the other hand, of course, if the first point to freeze was where there was a fitting, or stop cock, and there was a length of pipe which was subjected to freezing temperatures with a solid closure at the far end, then eventually the pressure build-up would be such as to burst the tube. Under these conditions the relative bursting point of a galvanized iron pipe will be higher than that of a corresponding copper pipe, so that marginally less failures might occur with galvanised iron. On the other hand, the chances of a plug of ice moving in a galvanized iron pipe is remote, so that from this point of view more failures would be likely to occur with galvanized iron than with copper.

Summarizing the position, you have to emphasize that layout and exposure conditions are extremely important and that the cause of bursting is pressure generated by the conversion of water to ice and that this pressure can be transmitted hydraulically in the usual way. The freezing itself is not a danger, except for the generation of this pressure, it is not the distension of the of the tube by the ice but rather the distension of the tube by water under pressure which causes the problem. Depending on the exposure conditions, bursts are less likely to occur under some circumstances with copper because of the smoothness of the bore.

Research into the mechanism of pitting corrosion has been undertaken by the copper industry in many countries of the world. Pitting occurs typically in cold, aerated, hard, organically pure waters from deep wells or boreholes and not in surface waters as generally used.

Borehole water and surface water can vary widely throughout the different areas of South Africa. The only regulations relating to potable water at present are those of the SANS which are classified as guidelines/recommendations and cover the health aspect rather than a corristivity with relation to any type of tubing used for reticulation of the water. Not all borehole waters are corrosive to copper or other types of available tubing, but a good general rule would be to have the water tested before selecting the type of tube to be used to ensure maximum durability of the installation.

Considerable research has been conducted on the effect of concrete on the corrosion of copper tubes and to quote from an International Copper development Council report: technical report Number 201 "copper tubes in ordinary Portland cement or concrete made with it do not suffer corrosive attack, but from an uniform adherent oxide layer. Similarly concrete with calcium chloride added has no corrosive effect even when the set concrete is kept intermittently or permanently wet.

An element often overlooked when considering the coupling of dissimilar metals is carbon. Practically all metals when coupled to carbon under the correct conditions would become anodic.

It would therefore be advisable to guard against the use of copper with ash bricks or cinders when used as backfill or the contamination of sand or concrete mix with ash from on-site open fires.

Under these conditions, with a strong electrolyte present, active galvanic cells could be set up and localised corrosion of the copper tube could take place resulting eventually in failure