Core TradesQuestion 191 of 700
What is the MINIMUM drain size generally required for a water closet (toilet)?
a.1-1/2 inches
b.2 inches
c.3 inches
d.4 inches
Explanation
A water closet requires a minimum 3-inch drain to carry its solid waste discharge. 1-1/2 and 2 inches are used for smaller fixtures such as lavatories and showers, and 4 inches, while acceptable, is larger than the required minimum for a single toilet.
Law Reference: 2025 CA Plumbing Code, Chapter 7 (Sanitary Drainage)Practice all 700 questions free — no signup required.
Related questions on this topic
- When the static water pressure supplied to a building exceeds what value, a pressure-reducing valve is generally required?
- A 4-inch horizontal building drain runs 48 feet at a minimum slope of 1/8 inch per foot. What is the total fall over that run?
- Why does the plumbing code prohibit the use of an 'S-trap' on a fixture?
- When a check valve or pressure-reducing valve creates a 'closed' water system, a thermal expansion tank is required PRIMARILY to:
- Under current California requirements, newly constructed dwellings must generally provide:
- Using the all-outdoor two-permanent-opening method at a rate of 1 square inch per 4,000 Btu/hr per opening, what is the MINIMUM net free area of EACH opening for a 100,000 Btu/hr furnace?
Last reviewed: · editorial process
PrepPass Editorial Team · Verified against California CSLB General Building (B) Trade Examination · How we review