TECHNICAL 33
Water reticulation : Selection of tubing
Edited by
Rory Macnamara
This is the first in a series on copper tubing and its correct application , extracted from the Code of Practice booklet published by Maksal . It must be noted that SANS 460 is the compulsory standard to be referenced in relation to copper .
All three classes of tubing as well as the ‘ economical ’ tube can be used with the capillary 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 O is recommended for all above-ground work , as its use would provide the maximum cost saving benefit . It is emphasised that Class 0 tubing is hard drawn , and any change of direction should be made with fittings . Local annealing of Class 0 to produce a bend is not recommended .
When compared with traditional systems , capillary systems can realise an installation time saving of up to 70 %.
Class 1 and 2 both 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 tubes bent by hand should have a radius of at least six ( 6 ) times the outside diameter of the tube and machine bent tubes should have a radius of not less than three ( 3 ) times the outside diameter of the tube .
Any deviation from the above figures could cause a restriction in the tubing producing turbulent flow and the possibility of erosion corrosion .
It is most important to remember that 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-degree 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 ’ s excellent internal corrosion resistance , tube bores remain smooth and internal diameters constant , thus eliminating the need to account for bore reduction of roughening when computing friction losses as with steel piping .
Copper ’ s light weight facilitates shipment , fabrication , and installation . Copper is compatible with all types of piping . It is accepted practice to join copper tubing to galvanised pipe , provided that the copper is downstream from the galvanised pipe . Certain corrosion problems may be experienced under specific conditions if the copper tube is connected upstream .
When cutting copper tubing with cutters or a hacksaw , care should be taken to produce a square end and to remove the burr produced . This will remove the turbulent flow , which could promote erosion corrosion . PA
Copper , before its many uses .
Copper Development Association
May 2022 Volume 28 I Number 3 www . plumbingafrica . co . za