Direct cold water supply
In this type of direct piping system, the entire of the cold water to the sanitary fitting is supplied directly from the service pipe. In order to provide a good main supply and pressure, the direct system has to be used with high level reservoirs and this is widely used in northern districts. With this type of piping system, only a small cold water storage cistern to feed the hot water tank is required and this can normally be located or placed below the roof ceiling level giving a saving on pipe runs to the roof space and eliminating the need to insulate the pipe against frost.
Another advantage of the direct piping system is that drinking water can be made available from several outlet service points. The main drawback is in case of repairs for direct piping system, the reserved main supply have to be cut off, also the supply level will be in the lower level during peak demand periods.
When sanitary fittings are connected directly to a main supply there is always a risk of contamination of the main water by back siphonage. This can occur if there is a negative pressure on the main and any of the outlets are submerged below the water level, such as a hand spray connected to the taps.
Indirect Cold Water Supply
For indirect water supply system, except for a drinking water outlet at the sink, all the sanitary fittings are supplied indirectly from a cold water storage cistern located at a higher level, usually in the roof space. This system requires more pipework but it gives a reserve supply in case of main supply failure and it also reduces the risk of contamination by back siphonage. The local water authority determines the system to be used in the area and they should be notified.
Pipework
Any of the materials which are suitable for the service pipe are equally suitable for distribution pipe and the choice is very often based on individual preference, initial costs and possible maintenance costs.
Copper Pipe
Copper pipe have a smooth bore giving low flow resistance, they are strong and can be easily jointed and bent. Joints in copper pipe can be made by one of three methods:
i) Manipulative compression joint – the end of the pipe is manipulated to fit into the coupling fitting with the help of a special tool. No jointing material is required and the joint offers great resistance to being withdrawn. It is usually by law requirement that his type of joint is used on service pipe under the ground.
ii) Non manipulative compression joint – no manipulation is required to the cut end of the pipe, the holding power of the joint relies on the grip of a copper cone wedge within the joint fitting.
iii) Capillary joint – the application of heat makes the soft solder contained in a groove in the fitting flow around the end of the pipe which has been cleaned and coated with a suitable flux to form a neat, clean and rigid joint.
Steel Pipe
Steel pipe for domestic water supply can be obtained as black tube, galvanised or coated for underground services. The joint of the steel pipe is usually made with a tapered thread and socket fitting, to ensure a sound joint from the steel pipe, stranded hemp and jointing paste should be wrapped around the thread; alternatively a non contaminating white plastic seal tape can be used.
Poly Pipe
Poly pipe is very light in weight, easy to be joint, non toxic and is available in long lengths, which gives a saving on the number of joints required. Jointing of poly pipe is common of the compression type using a metal of plastic liner to the end of the tube. To prevent undue sagging, poly pipe should be adequately fixed to the wall with saddle clips, recommended spacing are 14X the outside diameter for horizontal runs and 24X outside diameter for vertical runs.
Unplasticised PVC Pipe (UPVC Pipe)
This is type of plastic pipe for cold water services which is supplied in straight lengths up to 9m long and normally coated with grey, blue and black colours. Jointing of UPVC pipe can be by a screw thread but the most common method is by solvent welding. This involves cleaning and chamfering the end of the UPVC pipe which is coated with the correct type of cement and pushed into a straight coupling which has also been given a similar coat of cement. The solvent can be set within few minutes but the pipe joint does not achieve its working strength for 24 hours.
Cast Iron Pipe
In order to reduce the noise significantly, use neoprene gasket and hubless coupling with iron pipe is the best piping combination. The sound generated by this combination of piping would be muffled rather than being transmitted or amplified. The neoprene plays a vital role where it is used to separate the cast iron pipe from the fitting suppresses contact related sound. Cast iron pipe also can be said is the best performance in the piping family, and it is designed to best suit for sanitary and storm drain, waste and vent piping.
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