ANS:D - Glazed stonewares.

Glazed stoneware pipes are ceramic pipes that have been treated with a glaze, a glass-like coating, typically applied to the inner and outer surfaces of the pipe. This glaze provides several beneficial properties for sewage and drainage systems:

1. Smooth Surface: The glaze creates a smooth surface both inside and outside the pipe. This smoothness reduces frictional resistance to the flow of sewage, allowing for efficient conveyance of wastewater and minimizing the likelihood of blockages.
2. Resistance to Corrosion and Abrasion: Glazed stoneware pipes have excellent resistance to corrosion and abrasion, making them durable and long-lasting in sewer systems. They can withstand the chemical and physical stresses associated with the transport of wastewater over time.
3. Chemical Inertness: Stoneware pipes are chemically inert, meaning they do not react with the substances commonly found in sewage and wastewater. This inertness helps maintain the integrity of the pipe material and prevents contamination of the wastewater.
4. Tight Joints: Glazed stoneware pipes are typically manufactured with tight-fitting joints, which reduce the likelihood of leakage and infiltration of groundwater into the sewer system. This helps maintain the efficiency and effectiveness of the sewer system.
5. Ease of Installation and Maintenance: Glazed stoneware pipes are relatively easy to install and maintain compared to some other pipe materials. They can be cut and fitted easily on-site, and repairs or replacements can be carried out with minimal disruption to the sewer system.
6. Resistance to Biological Growth: The smooth glazed surface of stoneware pipes resists the adherence and growth of biological organisms such as algae, fungi, and bacteria. This helps prevent the formation of biofilms and reduces the risk of clogs and odors in the sewer system.

Due to these properties, glazed stoneware pipes are commonly used in sewer systems for house connections, lateral lines, and other applications where durability, longevity, and efficient conveyance of wastewater are important considerations. However, it's essential to ensure proper design, installation, and maintenance practices to maximize the performance and lifespan of glazed stoneware pipes in sewer systems.