Stoneware sewers (vitrified clay pipes) are commonly manufactured in a range of small diameters. Which of the following nominal sizes are commercially available for municipal house connections and laterals?

Introduction / Context:
Stoneware (vitrified clay) sewers are widely used for house connections and short laterals because they are resistant to corrosion from sulfides and domestic sewage. A frequent exam point is recognising the standard nominal diameters in which these pipes are commonly supplied.

Given Data / Assumptions:

• The question concerns commercially available nominal sizes for stoneware sewer pipes.
• Context is municipal wastewater systems (house connections and small laterals).
• Options list 10 cm, 15 cm, 20 cm, and 25 cm sizes.

Concept / Approach:
House service connections typically begin at small diameters due to relatively low flows. Traditional catalog sizes for vitrified clay include 100 mm, 150 mm, 200 mm, and 250 mm, matching the listed metric values. These sizes balance hydraulic capacity, maintenance practicality, and availability of fittings and joints.

Step-by-Step Solution:
Identify common nominal diameters for stoneware: 100, 150, 200, and 250 mm.Map to options: 10 cm, 15 cm, 20 cm, and 25 cm.Since all listed sizes are standard, the correct choice includes all items.

Verification / Alternative check:
Typical procurement schedules and BIS-style specifications show the same nominal diameter series for vitrified clay, confirming the completeness of the list provided in the options.

Why Other Options Are Wrong:
Any single-size choice omits other equally standard sizes and is therefore incomplete.

Common Pitfalls:

• Confusing minimum permitted sewer diameters (for public mains) with commercially available pipe sizes for house connections.
• Assuming availability only in one or two sizes; in practice, multiple sizes exist for graded capacities.

Final Answer:
All of the above