We estimate an aggregate daily water demand for Sydney using rainfall, temperature, and price data for the period 1994-2005. The estimated demand is used to calculate the difference in Marshallian surplus between using the metered price of household water to regulate total consumption in Sydney versus mandatory water restrictions for the period 2004/2005. Using a choke price of $5.05/kL for outdoor water demand, equal to the levelised cost of supplying and storing rainwater in a household water tank, we calculate the loss in Marshallian surplus from using mandatory water restrictions to be $235 million for the period 1 June 2004 to 1 June 2005. On a per capita basis this equates to approximately $55 per person or about $150 per household — a little less than half the average Sydney household water bill in 2005.