For the internal hot water distribution plumbing system of a high-rise residential building, which plastic material is the most appropriate selection due to its superior thermal resistance?
- AUPVC (Unplasticized Polyvinyl Chloride)
- BHDPE (High-Density Polyethylene)
- CCPVC (Chlorinated Polyvinyl Chloride)Correct
- DLDPE (Low-Density Polyethylene)
Solution
Concept
CPVC pipes for hot water systems
Formula
NONE
Step-by-step solution
1. Polymeric pipes are selected based on operating temperature and pressure ratings. 2. Standard UPVC pipes have a maximum service temperature limit of around 60°C and soften when conveying hot water. 3. Chlorinated Polyvinyl Chloride (CPVC) undergoes post-chlorination that increases heat deflection temperature up to 93°C (200°F). 4. Therefore, CPVC is the most appropriate plastic material for domestic hot water plumbing. Answer: C
Explanation
Chlorinated Polyvinyl Chloride (CPVC) is produced by post-chlorinating PVC resin, which raises its glass transition temperature and working temperature limit up to approximately 93°C (200°F). Conventional UPVC and HDPE pipes lose mechanical strength and degrade under continuous domestic hot water distribution. Consequently, CPVC is the industry standard plastic pipe material for hot water plumbing.
Why the other options are wrong
A) UPVC loses strength above 60°C and is restricted to cold water distribution and drainage. B) HDPE has limited high-temperature resistance and high thermal expansion for indoor hot water lines. D) LDPE has low strength and melting point, making it unsuitable for pressure plumbing.
Shortcut
CPVC = Hot & cold water plumbing; UPVC = Cold water and drainage only.
Common mistake
Selecting UPVC or HDPE for hot water piping, which softens and fails under high temperatures.
Correct answer: C) CPVC (Chlorinated Polyvinyl Chloride)