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By: FlowGuard EMEA on Aug 20, 2019 9:08:00 AM
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The Effects of Hot Water on CPVC and PPR Piping

Heat is used to shape and mold plastics, including CPVC and PPR, into the pipes and fitting used throughout a home or villa’s plumbing system. After processing, how a plastic material reacts to exposure to heat, mainly from hot water and the surrounding environment, differs based on the type of plastic and how it was processed.

When choosing the plastic piping material for your plumbing system, it is important to consider how heat, specifically hot water can affect it.

Maximum Allowable Operating Pressure and Temperature Rating of Plastic Piping

All plastic piping have a maximum allowable operating pressure rating at which the piping system may be operated for 50 years, and it is related to the water temperature. As the temperature increases, the maximum allowable pressure rating decreases to a point where the pipe can not handle the water temperature anymore, and this temperature is called maximum allowable operating temperature.

PPR’s maximum allowable operating temperature is 70°C for 50 years, which is around the same temperature that hot water reaches in most homes.

Schedule 80 FlowGuard® CPVC, on the other hand, has a higher allowable operating temperature of 93° C. This means that FlowGuard CPVC will keep its strength and appearance and last longer well beyond the temperature most pipes are exposed to in residential homes.

How Heat Leads to Corrosion

Heat is also an accelerant for corrosion. Over time, the susceptibility of a piping materials to corrosion is only going to increase when exposed to hot water.

In the case of PPR, the chlorine and chlorine dioxide used to disinfect drinking water corrodes the piping material. When chlorine is added to water, it transforms to hypochlorous acid, which is capable of breaking the carbon-to-carbon bonds of PPR’s polymer chain. The hydrogen atoms surrounding the carbon chain of PPR are small atoms which are incapable of protecting its chain from attack by hypochlorous acid.

This corrosion is more prevalent in hot water lines, because the heat makes the chlorine more active and also allows more penetration into the material. Over time, the degraded material erodes away and the pipe wall thins, weakening it and leading to leaks.




The image below shows the effects of hot chlorinated water on PPR pipe, with significant erosion of the pipe wall after only 9 months.



On the other hand, CPVC’s carbon chain is surrounded by large chlorine atoms which protect the chain from attack by the hypochlorous acid present in the water supply and significantly limit the effects chlorine can have on the material. Any chlorine that reaches its backbone will simply chlorinate it further which means that CPVC will maintain its strength and durability long term, even in chlorinated water at elevated temperatures.



The CPVC plumbing pipe on the right in the below image was in service in handling chlorinated drinking water for 23 years, and its wall thickness is still comparable to the new pipe shown on the left.



FlowGuard CPVC is Engineered for Hot Water Applications

FlowGuard CPVC is a reliable choice for residential plumbing applications. Due to its resistance to chlorine corrosion and heat distortion temperature well above normal potable water levels, it is ideal for use in hot water lines in homes in Africa and across the globe.

Have questions or looking to learn more about how FlowGuard CPVC can benefit your plumbing system? Contact our team of piping systems consultants.