Preliminary results from a Water Research Foundation study have found that annual single-family water use has decreased over the past 15 years. Reductions in both indoor and outdoor water use were measured.
For example, 34 percent of study homes in Denver had an average toilet flush volume less than 2 gallons per flush (gpf) indicating they are largely equipped with ultra-low-flush or high-efficiency toilets. Meanwhile, 26 percent of the homes had no flushes in the low-volume range. The remaining 40 percent of the homes had a mixture of low volume and older high volume toilets.
This is the third time end use data has been collected from a representative random sample in Denver and there has been a steady decline in the average toilet flush volume as older fixtures have been replaced. The results show progress in flushing efficiency, but also indicate that conservation potential remains in the toilet category.