In a national online survey, 1,020 participants reported their perceptions of water use for household activities. When asked for the most effective strategy they could implement to conserve water in their lives, or what other Americans could do, most participants mentioned curtailment (e.g., taking shorter showers, turning off the water while brushing teeth) rather than efficiency improvements (e.g., replacing toilets, retrofitting washers). This contrasts with expert recommendations. Additionally, some participants are more likely to list curtailment actions for themselves, but list efficiency actions for other Americans. For a sample of 17 activities, participants underestimated water use by a factor of 2 on average, with large underestimates for high water-use activities. An additional ranking task showed poor discrimination of low vs. high embodied water content in food products. High numeracy scores, older age, and male sex were associated with more accurate perceptions of water use. Overall, perception of water use is more accurate than the perception of energy consumption and savings previously reported. Well-designed efforts to improve public understanding of household water use could pay large dividends for behavioral adaptation to temporary or long-term decreases in availability of fresh water.