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Gary Dobson and Lee Flood of BPF Pipes Group explain why properly designed, installed and tested plastic piping systems are ideal for many hot and cold water applications.
Gary Dobson is Technical Consultant at Wavin, and Lee Flood is Director of Quality at John Guest. Both companies are BPF Pipes Group members.
The service life of plastics is generally determined by a combination of three factors; temperature, stress (pressure) and aggressive chemicals. Members of the BPF Pipes Group have piping products which undertake extensive testing at the extreme limits of these factors to ensure that they will give excellent performance in water systems.
In the UK, the service conditions for standard domestic applications can be found in BS 7291 “Thermoplastics pipe and fitting systems for hot and cold water for domestic purposes and heating installations in buildings.” These conditions are called ‘Class S’ and are as follows (Table 1 taken from BS 7291-1: 2010):
|Application||Nominal system flow temperature
|Maximum system service temperature
|System malfunction temperature
|System maximum working pressure A)
|Indirect cold water systems||20||20||–||3½|
|Direct mains-fed cold water systems||20||20||–||12½|
|Subsurface heating systems||60||83||100||3½|
|Vented hot water supply systems||65||83||100||3½|
|Unvented hot water supply systems including Instantaneous heaters and/or incorporating storage||65||95||100||6|
|Vented central heating systems and indirect hot water primary circuits||82||95||100||3½|
|Sealed central heating systems and indirect hot water primary circuits||82||105||114||3|
|Continuously operated re-circulating systems are excluded from these applications
A) Where a nominal working pressure does not comprise an integer value, the mantissa is expressed in a fractional format. This is done to reduce the possibility of misinterpretation or obscurity that could cause a system to be subjected to an excessive pressure.
B) 1 bar = 105N/mm2 = 105Pa
This standard (in common with the European Standards for plastics piping systems for hot and cold water installations) includes many tests which prove suitability for these applications. The tests are designed to replicate the conditions experienced by the pipe system in use at the limits of performance. These include:
Other short-term tests are designed to give manufacturers confidence that their piping system continues to meet the requirements on a day-to-day basis. These are basic pressure tests (at raised temperatures) over a short timeframe.
Factors in installation which can affect the lifetime of a plastics piping system
All members of the BPF Pipes Group provide extensive technical assistance on the correct installation of their systems. This information will help installers and end users maintain a correctly functioning system that will give many years of satisfactory service. Further assistance can also be found in Building Regulations and installation standards BS EN 806 “Specification for installations inside buildings conveying water for human consumption” and BS 8558 “Guide to the design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages – complementary guidance to BS EN 806.”
In summary, the main advice points from manufacturers are:
TESTING AND COMMISSIONING
When these sensible precautions are considered, plastics piping systems provide excellent performance in water systems over a long lifetime.