Back flow prevention devices should be inspected and re-certified annually by a licensed inspector. Texas may not pay attention to the federal requirements on this, but they certainly do in the state of Washington. In my city, those of us using city water for irrigation are provided a list of approved certified inspectors each spring (got my list about a month ago) It is our responsibility to contact one of these and make an appointment for inspection. If the inspector finds a device is not holding, he should have the repair parts necessary to make needed repairs on the spot. We pay the inspector's fee, usually $35, plus any repairs needed. He then sends a copy of his inspection to the city. If we fail to get the inspection, our water is shut off.