What is the correct requirement for a cleanout for underground drainage systems?

For underground drainage systems, a critical requirement is that cleanouts must be gas and water tight. This ensures that no gases or liquids can escape from the drainage system, which is particularly important for maintaining sanitary conditions and preventing contamination. The integrity of the cleanout is vital in preventing leaks that could create health hazards or environmental issues.

In addition, gas and water tightness is essential to keep pests and undesirable odours from entering the building through the drainage system. This standard reflects the principles of safety and function that underpin plumbing codes, prioritizing a safe and efficient drainage system.

While visibility above ground, location below the frost line, and access from above might be relevant factors in certain contexts, they do not address the fundamental necessity of maintaining the tightness of the system to prevent leakage and ensure function, which is why gas and water tightness is the primary concern for underground cleanouts.