Please note that this is for your own safety. It keeps you from drinking water that's been contaminated by nasty things such as animal feces, dead critters, fertilizers, or even pesticides. It keeps you from being sued by your neighbors if they get sick. As it is a law in Texas, even rural areas, we have to abide by it. $100.00 for a PVB with fittings is cheap for the piece of mind.
§344.50. Backflow Prevention Methods.
(a) Any irrigation system that is connected to a public or private potable water supply must be connected through a commission-approved backflow prevention method. The backflow prevention device must be approved by the American Society of Sanitary Engineers; or the Foundation for Cross-Connection Control and Hydraulic Research, University of Southern California; or the Uniform Plumbing Code;