Plastics materials. Pipes made of a number of thermoplastics materials are suitable for conveying the discharges from sanitary appliances (also rainwater). Such pipes are termed ‘discharge pipes’ in the relevant C.P. These include unplasticised polyvinylchloride (uPVC), polypropylene (PP), acrylonitrile butadienestyrene (ABS), polythene-sometimes referred to as polyethylene (PE). All these materials are light in weight and consequently easy to handle and highly resistant to corrosion. Their co-effi cients of expansion are, however, much higher than those of metals and proper and adequate allowance must be made for thermal movement. uPVC is the most commonly used plastics material for the larger diameter discharge and ventilating pipes, but should not be used where large volumes of water are discharged at temperatures exceeding 60 deg. C. The short term full bore discharges from some appliances may be at much higher temperatures e.g. some types of washing machines discharge water at 80 deg. C or even higher and the risk of distortion in uPVC pipes is correspondingly greater. Jointing may be accomplished by simple solvent welding, in which case expansion joints may be incorporated in the system. ABS pipes can be used in much the same way as uPVC, but have the advantage of being suitable for conveying discharges at higher temperatures. Polythene pipes, both high and low density, are used mainly for laboratory installations and certain small diameter waste pipes. They are more fl exible than uPVC, less liable to impact damage and are resistant to damage by freezing but need adequate support. Jointing is by welding or by mechanical means. Polypropylene pipes can be used in much the same manner as polythene pipes, but they are suitable for conveying discharges at higher temperatures. The correct grade must be used-consult manufacturer(s). Important Note: Plastics pipes for S.W. and V. pipes have been available commercially for many years and it must be recognised that pipes and fi ttings will continue to be ordered by ‘systems’ as offered by various manufacturers. It is not yet possible to provide a standard that would permit complete interchangeability of one manufacturer’s products with those of another. In fact, conditions of sale often include “…the Company will not be responsible for the malfunctioning of any installation, which includes plastics components not supplied by the Company”. Model Specifi cations are suggested such as “Supply XYZ Ltd. ABS soil and waste pipes and fi ttings in accordance with the architect’s drawings and fi x generally according to the manufacturer’s instructions”.