Which type of trap is legal for use in plumbing installations?

The answer pertains to anti-siphon traps, which are designed to prevent siphoning of water from the trap during drainage. These traps are crucial for maintaining proper water seals, ensuring that sewer gases do not enter the living spaces of buildings. Anti-siphon traps utilize a design that allows air to enter the system, breaking any siphon action and preserving the water seal.

In contrast, traps with moving parts, building traps, and grease traps may present issues in plumbing installations. Traps with moving parts can be prone to malfunction and may not allow for reliable sealing against sewer gases. Building traps, while they were used historically, are often seen as outdated in modern plumbing due to their potential to trap solids and cause backups. Grease traps are specifically designed to separate grease and fats from wastewater; however, they may not function as conventional traps intended for general waste drainage.

Overall, the functionality and maintenance advantages of anti-siphon traps make them the preferred legal choice in plumbing installations.