Plumbing Factors [Mar 2012]

March 22, 2012 5:40 am

Today, plumbing has emerged as an indispensable element in building designing. However, the efficiency of plumbing depends to a large extent on the usages of appropriate methodology and effectiveness of plumbing materials involved. According to the experts in this niche sector, following factors to be considered in selecting a piping system for plumbing:
• Pressure Rating & Long term Performance• Toughness & rigidity of the material• Thermal conductivity of the material• Thermal contraction and expansion of the material• Ease of Installation & reparability• Effect of disinfectants on the material• Hygiene & suitability for use in portable water• UV stability (External usage)• Fire Properties.Pressure Rating & Long term PerformanceAssumption: Service life of 50 years.
CPVC: SDR 11
SDR 13.5
Pressure rating
@ 23°C
28.2kg/cm2
22.5kg/cm2
Pressure Rating
@ 93°C
5.7kg/cm2
4.5kg/cm2
PPR PN 20
PN 16
Pressure Rating
@ 23°C
24.2kg/cm2
20 kg/cm2
Pressure Rating
@ 93°C
3.5kg/cm2
3 kg/cm2
For the same pressure ratings PPR uses higher wall thickness compared to CPVC resulting in lower inner diameter. Hence it can be stated that in case a cost comparison is made between CPVC and PPR, PPR should be taken one size higher to CPVC i.e. if CPVC taken is ½”, PPR should be taken is ¾”and so on.
Toughness & Rigidity of the materialCPVC has a much higher strength / modulus than other thermoplastics.                                     CPVC                    PPRTensile Strength             55Mpa                    30Mpa
This means that CPVC:• Needs less hangers and support• There is no unsightly ‘looping’ of the pipe• More suitable for vertical risers.Impact Strength: PPR has a slightly better impact strength than CPVC. However it has to be noted that plumbing pipes are not subject to impact loading which is a property prior to installation and not once the pipes are installed in place.
Thermal Conductivity of the Material                                        CPVC              PPRThermal Conductivity          0.14W/MK        0.21W/MK
Again CPVC scores over PPR due to the latter’s high thermal conductivity and hence poor insulation properties.
Thermal contraction and expansion of the materialCoefficient of                  CPVC                      PPRThermal Expansion        0.7×10-4mm/MK        1.5 x10-4mm/MK
Here, CPVC scores over PPR due to its low coefficient of thermal expansion which helps in reducing the amount that the pipe expands when hot water is running, again reducing unsightly ‘looping’ of the CPVC pipe compared to PPR Pipes.
Ease of Installation & ReparabilityCPVC uses a simple, solvent cement jointing method commonly known as Cold Fusion. Tools required are very simple and inexpensive. Installation is easy in tight, confined or inaccessible places. The basic installation procedure is the same as that for PVC – known and used by virtually all plumbers.Reparability: Very easy, without need of any special equipment.Authenticity of the joint: Solvent cement joining is not an adhesive joining but is the cold fusion in which the solvent cement melts the top of the pipe and the inside of the fitting which then fuse into each other forming a monolithic seamless joint.In case of PPR, it uses Heat Fusion method. A heating device is required and source of electricity is a must. It has been observed even in the best of installations of PPR that due to some leniency from the end of the plumbers a bead formation takes place reducing the inner diameter of the fitting resulting in pressure loss. At many sites, it has also been observed that there is total blockage in the fitting due to improper installation which is very difficult to detect.
Effect of disinfectant on the materialCPVC has been in use in USA since the last 50 years and USA use chlorine as a disinfectant for water purification. CPVC technology was invented in USA and it has been working well in all countries using chlorine / ozone etc.
PPR is a Polyolefin based plastic and studies done by a number of independent test institution have generated data which demonstrates without doubt that small quantities of chlorine exhibit a strong oxidising effect on polyolefin pipe (PB, PE- AL-PE , PPR, PEX ) resulting in a significant reduction of the expected life time.Hence countries like USA came up with an American Standard i.e. NSF p 171 Protocol for chlorine resistance of plastic piping materials and ASTM F-2023-04 to counter this problem.
Hygiene & suitability for use in portable waterCPVC: International studies have shown that CPVC has the lowest bacterial growth, compared to steel, copper and any alternate plastic piping material. Also studies have shown that CPVC is the clear winner as it does not deteriorate the quality of water under extended stagnation conditions compared to steel and copper piping.
Biofilm concentration is the lowest compared to all piping material. CPVC is unaffected by the chlorine in water and there is negligible additive migration from the piping material to the water supply.
FlowGuard CPVC is NSF certified for portable water use. Solvent cement for joining is also NSF certified for portable water use.
PPR: Polyolefin has the tendency to oxidise and to prevent oxidation it require high levels of antioxidants. These may leach into water supply, causing bad odour and taste problems.
Many PPR pipes allow light transmission through the body of the pipe which propagates the growth of bacterial. Bacterial and fungus growth have been noted in many cases in PPR pipes in India which has forced many PPR manufacturers to modify their pipes by introducing an anti-bacterial layer, or use an additives which sanitise the basic PPR material to counter bacterial growth.UV Stability (for external exposed piping)CPVC: The main degradation process is dehydrochlorination, not oxidation. This dehydrochlorination, whilst slightly accelerated by UV, does not break down the polymer chains to any significant extent after outdoor exposure, being mainly limited to a surface discoloration effect.• No significant loss in pressure bearing capability• 45 years of outside service in Southern California, 8 years trouble free installations in India and also more than 15 years in Middle East.
Polyethylene Polypropylene: UV acts as a strong catalyst for the oxidation process which breaks down polymer chain, leading to weakness in pipe and loss of hydrostatic strength. PPR manufacturers have different UV protect covering on the pipes which are more expensive than the regular piping and alternatively they recommend encasing of the PPR pipes in a thin layer of PVC pipe to protect against UV radiation.
Fire PropertiesLOI (limiting oxygen index) is defined as the amount of oxygen required by an item to burn in atmosphere. For CPVC the LOI is 60 and hence CPVC does not support combustion. However, in the case of PPR the LOI is 18 and hence it not only supports combustion but drips fire adding to the fire load of the building.
Hence to conclude it can be derived that on all properties CPVC is the clear winner over any other thermoplastic for plumbing applications.(Inputs & image courtesy: Lubrizol India)