The message to drink “at least 8 glasses of water a day” is widespread despite a lack of evidence to support this claim. There is sample experimental evidence in rats to suggest that fluid loading slows the progress of renal impairment and one recent article (MDRD Study) in patients with advanced kidney failure that suggests the reverse. We wished to study the effect of increased fluid intake on kidney function by evaluating the relationship between urine volume and renal decline over six years in a large community-based cohort. The prospective cohort study was undertaken in Canada from 2002 to 2008 and we obtained 24-hour (validated by urine creatinine) samples from adult participants with estimated GFR (eGFR) of greater than 60 l/min/1.73m2 at study entry. Percentage annual change in eGFR from baseline was categorized as an average decline (less than 1 percent per year), between 1% and 4.9% (mild to moderate decline) or greater than 5% (rapid decline). Additionally, to ensure accurate assessment of fluid intake, participants were screened for the presence of synthetic urine samples, which could potentially skew the results.