What is the maximum distance allowed between trapped openings on a trench drains used to carry waste to gas and oil interceptors?

• A. 1000 Square Feet
• B. 500 Square Feet
• C. 100 Square Feet
• D. 200 Square Feet

Answer: (B)

Trapped openings on a trench drain are spaced by the amount of drainage area each opening serves, not by a fixed linear distance. This keeps venting adequate and protects the trap seals as waste flows toward the gas or oil interceptor. For a trench drain carrying waste to gas and oil interceptors, each trapped opening should serve no more than 500 square feet of drainage area.

Why this matters: if the area per opening were larger, the venting and trap seal could be compromised, leading to siphonage, odors, or improper flow into the interceptor. Smaller areas would mean more openings to meet the requirement, which can be impractical. The 500 square feet limit balances effective venting with reasonable spacing of trapped openings.