Under what condition can cleanouts be omitted on a horizontal drain line less than 5 feet?

Cleanouts in plumbing systems serve an essential purpose: they provide access for maintenance, cleaning, and inspection of the drainage lines. The decision to omit cleanouts is primarily based on the configuration and use of the plumbing fixtures connected to the drain line.

In the context of horizontal drain lines that are less than 5 feet, cleanouts can be omitted when the drain line serves sinks. This is because sink drainage typically involves shorter runs with less potential for clogs compared to other fixtures. Sinks are often fitted with trap assemblies that help catch debris and prevent clogs from moving further down the line, allowing for easier access for cleaning if necessary.

In contrast, other fixtures like toilets and floor drains generally present a higher risk for blockages or require more frequent maintenance due to their use, making cleanouts more necessary. Therefore, omitting cleanouts on horizontal drain lines less than 5 feet is specifically permissible for those that serve sinks, given their unique characteristics and lower likelihood of clogging issues.