[maybe]

I am north of 466 and have only one water bill that includes both the house and irrigation. The rate charged for water more than doubles after 11,000 gallons, yet it seems impossible to keep it under 11,000 unless one waters the lawn less than once a week. Is this correct?
Does anyone have an average size, non-corner, lot with an average size ranch house, and a green lawn, yet uses less than 11,000 a month all year?
I live alone and when sprinklers are off my water usage has been as low as 1000 gallons, so I don't have a leak in the household water lines..

[Dr Winston O Boogie jr]

Do you have a sensor that shuts the irrigation system off when it rains?

I would expect my water bill to go down when we start getting daily rain.

[rhood]

Our average usage year round is about 3000 gal. Has never been over 3500 gal. Lawn is green and in good condition. I only water manually when it needs it.

[rjm1cc]

Sounds like something is wrong with your system.
How many zones?
How long does each zone run? The time does depend on the type of spray heads so if you know what type.
My guess is there is a leak in one of your zones. Can you run each zone for say 10 minutes and read your water meter each time to see gallons used. If one zone uses a lot more water this might indicate a problem. I am assuming each zone is about the same size.