Consumer and building applications: Lavatory cisterns (water closets) are commonly manufactured from which polymer among the choices listed, owing to corrosion resistance and ease of molding?

Introduction / Context:
Plumbing products must resist water, household chemicals, and impact, while being economical and easy to fabricate. Modern cisterns and fittings often favor thermoplastics that can be injection-molded or blow-molded with integrated features and robust sealing surfaces.

Given Data / Assumptions:

• We focus on common mass-market cisterns (not ceramic tanks).
• Material needs: corrosion resistance, adequate stiffness, and compatibility with seals/valves.
• Options include several common polymers with different properties.

Concept / Approach:
PVC (particularly unplasticized PVC, uPVC) offers good chemical resistance, rigidity, and weldability/glue-ability for plumbing applications. It is widely used in pipes, fittings, and cistern housings. Other listed polymers either lack the necessary toughness/stiffness balance, are more expensive, or are used for different applications (e.g., perspex for glazing, EPS for insulation/packaging).

Step-by-Step Solution:

Verification / Alternative check:
Commercial plumbing catalogs and building-product specifications show uPVC cisterns and uPVC fittings as standard offerings.

Why Other Options Are Wrong:

• Perspex (acrylic): Brittle and costlier; used for windows/displays.
• Expanded polystyrene: Foam; not suited to pressurized water containment.
• Saturated polyester: Requires fiber reinforcement and different processing; not typical for cistern bodies.

Common Pitfalls:
Confusing ceramic/porcelain cisterns with polymer ones; the question specifically targets plastic cisterns.

Final Answer:
PVC