What is the minimum trap size for a urinal?

What is the minimum trap size for a urinal?

• A. 1 1/2" Minimum Trap Size
• B. 2" Minimum Trap Size
• C. 1" Minimum Trap Size
• D. 3" Minimum Trap Size

Answer: (A)

Trap sizing is about giving each fixture a trap that can hold a proper water seal while safely handling the discharge flow. Codes set minimum trap sizes for different fixtures based on typical usage and flow, so the trap isn’t too small to siphon or too large to waste space. For a urinal, the smallest trap that code typically allows is 1/2 inch? No—it's 1 1/2 inches. This size provides enough capacity to maintain the water seal during a flush and to resist siphoning, even when other drainage on the line is active. A smaller trap could lose its seal under normal or surge conditions, while a larger trap isn’t necessary for a single urinal and adds cost without added benefit. If the fixture load is higher (more urinals or specialized systems), the trap size can be increased, but the minimum remains 1 1/2 inch.

Trap sizing is about giving each fixture a trap that can hold a proper water seal while safely handling the discharge flow. Codes set minimum trap sizes for different fixtures based on typical usage and flow, so the trap isn’t too small to siphon or too large to waste space.

For a urinal, the smallest trap that code typically allows is 1/2 inch? No—it's 1 1/2 inches. This size provides enough capacity to maintain the water seal during a flush and to resist siphoning, even when other drainage on the line is active. A smaller trap could lose its seal under normal or surge conditions, while a larger trap isn’t necessary for a single urinal and adds cost without added benefit. If the fixture load is higher (more urinals or specialized systems), the trap size can be increased, but the minimum remains 1 1/2 inch.