Perception of social rank, or how we perform relative to our peers, can be a powerful motivator. While research exists on the effect of social information on decision making, there is less work on how ranked comparisons with our peers influence our behavior. This paper outlines a field experiment conducted with 5,180 households in Castro Valley, California, which used household mailers with various forms of peer information and social rank messaging to motivate water conservation. The experiment tests the effect of a visible social rank on water use, and how the cooperative and competitive framing of rank information influences behavioral response. Difference-in-difference and matching methods reveal sizable treatment effects of the mailers on household water use (reductions of 13-17 gallons per day, depending on mailer version). However, households with relatively low or high water use in the pre-treatment period responded differently to information framing. We find that neutrally-framed rank information caused a "boomerang effect" (i.e., an increase in average water use) for low water use households, but this effect was eliminated by competitive framing. At the same time, competitively-framed rank information demotivated high water use households, increasing their average water use further. This result is supported by evidence that the competitive frame on rank information increased water use for households who ranked "last" in the peer group - a detrimental "last place effect" from competitive framing.