Why does my residential water bill change twice a year?

Residential Water Meters are read and billed based on a valid reading twice a year. Historically, water usage during the winter and spring months is low so the remaining 10 months, your water usage is estimated based on a calculated 1,000-cubic feet times the current usage rate. During the 2 true-up billing months when a valid reading is entered, any usage over the allotted monthly 1,000-cubic feet will be billed to your account. Any over-estimated usage age will be credited to your account. Additionally, your bill will list the Read Type as “Valid” instead of “Estimated”.