Which plumbing fixture generally has the highest DFU value?

In plumbing, the Drainage Fixture Unit (DFU) value is a standardized measure used to quantify the waste discharge from various plumbing fixtures, allowing for the design and sizing of drainage systems. The toilet typically has the highest DFU value among common plumbing fixtures. This is largely due to its function and frequency of use, as a toilet discharges a significant volume of water with each flush, which is often more than what is discharged by other fixtures during typical use.

Toilets are designed to handle solid waste, which requires a substantial amount of water for effective flushing and waste transport through the drainage system. The standard DFU value for a toilet often reflects this higher discharge volume, accommodating the need for a robust drainage system capable of managing the significant load placed on it.

In contrast, showers, sinks, and bathtubs generally have lower DFU values because they handle less volume and frequency in comparison. Showers and bathtubs, while they use considerable water, do not flush waste in the same manner as toilets, resulting in lower DFU ratings. Sinks usually rank even lower due to their usage pattern and the nature of the discharge (primarily liquid waste from washing hands, dishes, etc.), further underscoring the toilet's