Which plumbing fixture commonly has the highest water usage?

Toilets, particularly older models, commonly have the highest water usage among plumbing fixtures. This is primarily due to their design and functionality. Traditional toilets from previous decades can utilize anywhere from 3.5 to 7 gallons of water per flush, significantly more than more modern, efficient models, which typically use about 1.6 gallons per flush or even less.

The high volume of water used per flush in older toilets contributes to their overall water consumption when compared to other fixtures. Showers and faucets typically have lower flow rates — showers often max out at around 2.5 gallons per minute, and faucets usually range from 0.5 to 2.2 gallons per minute, depending on aerators and usage. Dishwashers also have improved efficiency, often using efficient wash cycles that require significantly less water than multiple toilet flushes over a given time.

Thus, it is clear that older toilet models, due to their high per-use water consumption, represent the highest water usage among the listed plumbing fixtures, making them a crucial target for water conservation efforts.