All Durham soil and waste systems must be of which drainage type?

The proper drainage type for all Durham soil and waste systems is recessed. This design allows for efficient drainage by providing enough space for water to flow without obstruction, minimizing the risk of blockages. Recessed systems are also advantageous because they can accommodate the potential expansion of waste materials, reducing the likelihood of sewage backup and ensuring a more effective waste management process.

Other drainage types, such as plain or sealed, do not offer the same level of drainage efficiency required for waste systems. Galvanized systems are typically used for other applications and may not meet the specific requirements for drainage in Durham soil and waste systems, making the recessed design the most appropriate choice.